Facebook's Scary "Find a Friend" Algorithm



  • Like many people, I have Facebook, but rarely participate beyond commenting on someone's baby or engagement announcement, or making the occasional witty status message. The most I tell Facebook is where I went to school, and my work history, dating back to 2006. Other than that, it will have to detect things by checking out my friends.

    Facebook has its "people you may know" feature. Based on your who you know and what you've put on your profile such as work and educational history, it can go through its algorithms and make a pretty accurate guess. For some of these guesses, it's obvious how they've determined this result. It's either through a fair number of mutual friends or based on work history. Even if I don't provide work history, I bet Facebook can still surmise with some accuracy just by finding common employers among my friends who do give out that info. With others, it's got to be quantum computer-level clairvoyance. Let's take a look at these cases:

    Girl I had a single date with in 2007

    I had a match.com account. This account was not at all linked to Facebook, and my only communication with her was through email or AOL instant messenger. We were never facebook friends. She lived 50 miles away, having moved into her town from Virginia months prior. There were absolutely no connections between anyone I was ever affiliated with and her. We had a single date, which was fair, but there were no fireworks, so we moved on our separate ways, and she soon after moved back to Virginia, so it probably wouldn't have worked out anyways. It was such a non-eventful date, I didn't even tell anyone about it.

    Over 10 years later, she's in my suggested friends list. Still no mutual connections, we hadn't talked in ages, hell, I had even forgotten who she was and the only reason I recognized her was because she had a unique name.

    Possible reasons Facebook found her:

    a.) We probably searched for each other's profiles way back in 2007, and Facebook had this stored in its database this whole time, only to "helpfully" remind us of this fact way after it lost any relevance.

    b.) Facebook has some kind of hook into match.com, Gmail, and/or AOL and is stealing our thoughts.

    Person I had a brief business relationship with during a contract gig

    This dates back to 2004, before Facebook even existed. I had a website gig for a local business. One day a marketing exec from the local TV station called me to try to sell me something to plug with that business for TV ads. Said person had a working business relationship with the client, but he was reaching out to me because the product he was selling was very technical and my client was a luddite who didn't even own a computer, so there was no point in explaining what this thing was to him directly, but perhaps I could serve a purpose. I agreed to entertain the thought, if only to get a free tour of a TV station and a paid lunch, which was cool, but nothing really came of it afterwards.

    My correspondence, which lasted a few weeks, was only through two avenues: Phone call and my client's email, which was hosted on a private server. He had retired in 2005. Again, there was no connections between him and I on Facebook. I had left the contract before I even joined Facebook, and I never referenced the client or anyone affiliated with him in any of my posts.

    About 15 years later, he popped up on my suggested friends list. He has a mere 11 friends, all of which appear to be family and in-laws, he has a half-written profile that just mentions his alma mater. He joined Facebook about a year ago.

    Possible reasons Facebook found him:

    a.) ...no fucking clue. Our correspondence was brief, outside of Google, predates Facebook, we have no mutual connections, no mutual work history that Facebook should know about, and there'd be no reason for either of us to even search each other on Facebook years after our correspondence. This one is a true undefined that makes me wonder just what kind of deep analysis they are using to dig up these ghosts.


  • Grade A Premium Asshole

    Facebook does have a hook into plenty of popular e-mail providers, you can agree to it going through your entire e-mail account. I think it even prompts you to do that when you create a new account, or at least it used to. Some people seem to actually do that, hopefully just being unaware of how unbelievably invasive Facebook is being towards themselves as well as anyone they ever got an e-mail from.

    You can find it behind the Find Friends link in the top bar:

    0_1518027197769_Screenshot from 2018-02-07 19-12-26.png



  • @blek I don't think it's that. I never did that, knowing how much of a anti-privacy clusterfuck Facebook is. I use my gmail address as my username, but AFAIK there is no link between the two accounts other than that.


  • Grade A Premium Asshole

    @the_quiet_one Yeah, you didn't. They probably did, and Facebook doesn't ask your permission. I don't know how it's legal but they've been doing this as long as I remember.



  • @blek The only way for Facebook to gain access to my contacts on gmail is by logging into it. Unless you're saying they hacked my account, that's impossible. I never do any SSO shit with Facebook.

    Also, as I said before, the second guy had no correspondence whatsoever with my gmail account. He didn't even know my gmail address. He only talked to me via the non-google email account I had through the client.


  • Fake News

    @the_quiet_one No. @blek is saying that the people you "know" agreed to have their data rifled through.



  • @blek except they couldn't find it by email alone. They'd have to dig up an email chain from over decade ago, and figure out that this person and that person is the same. Depending on uniqueness of @The_Quiet_One's name, it's somewhere between extremely hard and literally impossible.



  • @lolwhat said in Facebook's Scary "Find a Friend" Algorithm:

    @the_quiet_one No. @blek is saying that the people you "know" agreed to have their data rifled through.

    @gąska said in Facebook's Scary "Find a Friend" Algorithm:

    @blek except they couldn't find it by email alone. They'd have to dig up an email chain from over decade ago, and figure out that this person and that person is the same. Depending on uniqueness of @The_Quiet_One's name, it's somewhere between extremely hard and literally impossible.

    Ah, yes. I see.

    Only problem with that theory is we corresponded through each of our work email addresses. Seeing that he retired over 10 years ago, I doubt he was using that email address with Facebook when he joined a year ago.

    My name is relatively unique, though, so I wouldn't rule out the possibility that through some crazy series of events they found something associated with him that had my name on it, saw that we were in the same general location geographically, and put 2+2 together. However, what's crazy about even that is Facebook found it to be a relevant enough connection that they'd actually notify me about it as if he was some long-lost best friend or something.



  • @the_quiet_one he might've been assigned relevance of 0.00001 but still end up in top 10 (depending on how often you meet new people vs. how fast you churn through suggested friends list).


  • Grade A Premium Asshole

    @the_quiet_one Oh. Well that's weird. I thought he had an e-mail from you that came from the address you registered at facebook with.

    Still I'm pretty sure it's related to the "Find Friends" thing. I used to have an account that was registered with my gmail and it kept suggesting people that I know I talked to over e-mail and who had no connection to me otherwise. My current account is registered using a 10minutemail address and this never happens, all friend suggestions are either through mutual friends or seem entirely random (people I've never heard of).



  • @gąska Well, I mean, when you get relevance levels of that, with all the noise and statistical margins of errors, they might as well suggest Tom Cruise as a friend. Hell, I even have someone on my friends list from college who currently works in a Hollywood studio office. You're basically playing 6-degrees to Kevin Bacon at that point. I have certain friends who literally oversaturated their friends list with over a thousand friends. Each of them should be automatically more relevant than a guy who likely had my name written in some archived email from 15 years ago.


  • Impossible Mission - B

    @the_quiet_one said in Facebook's Scary "Find a Friend" Algorithm:

    Well, I mean, when you get relevance levels of that, with all the noise and statistical margins of errors, they might as well suggest Tom Cruise as a friend.

    A friend of mine is Kevin Costner's cousin.

    (No, not that Kevin Costner. Other person with the same name. Much less famous.)



  • @the_quiet_one I don't use Facebook myself, but there was this big deal a few years ago about its Android app silently sucking in basically every bit of info on the phone-- that could include your historical emails from 2004 with business guy and possibly date arrangements?



  • @blakeyrat My correspondence with the second one predates smartphones, and I stopped using that email account long before getting any smartphone. At the time I think I had an old Nokia with a screen resembling a Game Boy.

    It may explain the first one, though. To be honest, the first one probably has a bit less mystery to it, since there is at least some different scenarios which may associate me with her, if only because one of us leaked email info to Facebook. Facebook thinking I'd be at all interested in this connection would be the only thing that's undefined.



  • I might be able to top that. Several years ago, Facebook suggested someone that, as far as I remember, I never communicated with outside of IRC. I still have no idea how Facebook figured that one out. That person is one of only two people that I'm connected to on Facebook that I've never met in person at least once (the other is a person in a local group that I just haven't met yet).

    And then there are the batches of ads that Facebook used to show in the sidebar of their feed page, which reassured me that Facebook can't figure out anything about me.



  • @blek said in Facebook's Scary "Find a Friend" Algorithm:

    I don't know how it's legal but they've been doing this as long as I remember.

    It's a well known secret that Facebook breaks pretty much every EU privacy law there is.
    Problem is you can't really prove it, so they'll get away with it.

    For example, there was this guy a few years ago who asked them to provide all the data they have about him, sued for it and won. He got many hundreds of pages of shit they had on him, and I'm not even sure he had a real profile or just a "shadow" profile.
    You could also ask them to delete all the data they have about you and other than, say, you have open bills or business relations with them, they'd have to comply. But really, how could you prove that they don't keep your data around anymore after you've "deleted" your account. So what they're doing is just "yeah sure, it's all gone undefined".



  • @dragnslcr said in Facebook's Scary "Find a Friend" Algorithm:

    And then there are the batches of ads that Facebook used to show in the sidebar of their feed page, which reassured me that Facebook can't figure out anything about me.

    They're just pretending.


  • kills Dumbledore

    @dragnslcr said in Facebook's Scary "Find a Friend" Algorithm:

    And then there are the batches of ads that Facebook used to show in the sidebar of their feed page, which reassured me that Facebook can't figure out anything about me.

    If you go to https://www.facebook.com/ads/preferences, you can see the "inferences" they've made in order to target ads, the most interesting of which is your political views if you're in the U.S. If Facebook seems like an "echo chamber", things like that may be why.



  • @the_quiet_one said in Facebook's Scary "Find a Friend" Algorithm:

    Only problem with that theory is we corresponded through each of our work email addresses. Seeing that he retired over 10 years ago, I doubt he was using that email address with Facebook when he joined a year ago.

    Scenarios:

    1. He joins facebook. Tries to friend some people who worked from Company A. Successful friend-ing or not, that's a connection. Company A people have connections to Company B ... Company N, which is the company you used to work for.
    2. He tried to search for you at some point, by name, and that made a connection. Maybe he didn't find you, or was just FaceStalking you, or you never saw his friend request.

  • Impossible Mission - B

    @topspin said in Facebook's Scary "Find a Friend" Algorithm:

    It's a well known secret that Facebook breaks pretty much every EU privacy law there is.
    Problem is you can't really prove it, so they'll get away with it.

    For example, there was this guy a few years ago who asked them to provide all the data they have about him, sued for it and won. He got many hundreds of pages of shit they had on him, and I'm not even sure he had a real profile or just a "shadow" profile.
    You could also ask them to delete all the data they have about you and other than, say, you have open bills or business relations with them, they'd have to comply. But really, how could you prove that they don't keep your data around anymore after you've "deleted" your account. So what they're doing is just "yeah sure, it's all gone undefined".

    Google: Don't be evil.
    Facebook: Don't even bother pretending we're not being evil.



  • @heterodox said in Facebook's Scary "Find a Friend" Algorithm:

    @dragnslcr said in Facebook's Scary "Find a Friend" Algorithm:

    And then there are the batches of ads that Facebook used to show in the sidebar of their feed page, which reassured me that Facebook can't figure out anything about me.

    If you go to https://www.facebook.com/ads/preferences, you can see the "inferences" they've made in order to target ads, the most interesting of which is your political views if you're in the U.S. If Facebook seems like an "echo chamber", things like that may be why.

    The best one I ever got had nothing political at all. One ad was for an MBA program (people here know most techies' opinion of MBAs), one was for Christian singles (Facebook knows I'm not Christian), and one was for "bad girls" (uhhh, yeah...). It was pretty hilarious.


  • Notification Spam Recipient

    If any WTDWTFers show up on your lists, then you can officially claim Skynet.



  • I feel like I'm safe in this regard. Facebook can't seem to find someone I met several times, don't know the last name of, and knew mostly by a pseudonym. There was some correspondence through a website I hope is now dead, but in any case, Facebook seems to know nothing.



  • @pie_flavor There are a few profiles in my list I have that I know I never met. Maybe they are some of you guys? :p



  • @lorne-kates said in Facebook's Scary "Find a Friend" Algorithm:

    @the_quiet_one said in Facebook's Scary "Find a Friend" Algorithm:

    Only problem with that theory is we corresponded through each of our work email addresses. Seeing that he retired over 10 years ago, I doubt he was using that email address with Facebook when he joined a year ago.

    Scenarios:

    1. He joins facebook. Tries to friend some people who worked from Company A. Successful friend-ing or not, that's a connection. Company A people have connections to Company B ... Company N, which is the company you used to work for.

    Again, 6 degrees to Kevin Bacon. I'm company N to virtually every company in thec world at that point. Why single him out from the millions of others connected similarly?

    1. He tried to search for you at some point, by name, and that made a connection. Maybe he didn't find you, or was just FaceStalking you, or you never saw his friend request.

    Unlikely. He was a marketing exec. He deals with tons of people throughout his career. I was a nobody in the grand scheme of his life. I didn't even fulfill his mission of selling his product to his client.



  • @pie_flavor said in Facebook's Scary "Find a Friend" Algorithm:

    If any WTDWTFers show up on your lists, then you can officially claim Skynet.

    I "friended" your mom.



  • @the_quiet_one said in Facebook's Scary "Find a Friend" Algorithm:

    Again, 6 degrees to Kevin Bacon. I'm company N to virtually every company in thec world at that point. Why single him out from the millions of others connected similarly?

    Maybe also you are over-focusing on one successful suggestion. How many other random people are suggested by Facebook, that you reject because you don't know them?

    I get the feeling that Facebook is playing 6-degrees, and suggesting huge lists of anyone (with some "AI" thrown in there, i.e. a pile of "ifs" to e.g. not suggest to you random celebrities unless you have a strong link, maybe over-prioritize people with the same surname as they are more likely to be family etc.), and the fact that once in a while it happens to suggest someone that you do actually know does not prove anything, except that they are kind of right in doing that...

    It's like this time when I randomly met at an event someone that I had not seen for at least 5 years, when we were both living in another country. No "scary stalker" stuff here, just that we randomly cross paths with thousands of people and once in a while a weird coincidence does happen.



  • @remi sure, but I don't actively reject suggestions, I merely ignore them. As a result, I still have suggestions that existed for years. And while they do rotate some if them out, it seems to be on a relatively infrequent basis (monthly? Not sure). So I would think I'd have to on a daily basis explicitly reject all my suggestion to get a new batch every day for the real obscure ones to start coming out.



  • @the_quiet_one Maybe. My point is mostly that we notice coincidences and tend to give them more weight/significance than the simple fact that they are just that, coincidences.

    Also, like others said, you are trying to explain these connections by looking only at your side of things, whereas Facebook obviously has both sides (i.e. yours and the suggested friend's one). You don't know if they happen to do something that would cause Facebook to believe that you would be a good friend suggestion for them, and because friendship is (often) reflective, it makes a lot of sense for Facebook to suggest them to you as well.



  • Oh look, a new one!

    The real-estate agent who sold the condo I bought over 10 years ago. Haven't spoken to her since the sale. This time the theory of my email being on her contacts list is moot because we only spoke over the phone and maybe via text. So, that leaves the possibilities being:

    • Facebook going through public records, finding the sale, and linking us that way.

    • She owns her real estate company, and is relatively popular in the area she sold to me in, and I know of at least 10 other people who bought houses in that area on my friends list in the last several years. Perhaps they found a connection between her and someone else who she did email that was in my friends list.

    • I'm her secret crush and she's been stalking me this entire time, leaving trails all over the internet for Facebook to pick up.

    Another note: Facebook must have "improved" its algorithm relatively recently. Up until a month or two ago, Facebook's suggested friends have always been pretty explainable, even if some of them were kinda a stretch. Most of the suggestions have mutual friends, but the suggestions they make that don't have mutual friends are almost entirely the ones like these, where they're doing some voodoo magic to find stuff.

    At the rate they're going, they'll somehow match adopted kids to their birth parents despite the sealed records.



  • @remi said in Facebook's Scary "Find a Friend" Algorithm:

    @the_quiet_one Maybe. My point is mostly that we notice coincidences and tend to give them more weight/significance than the simple fact that they are just that, coincidences.

    I would agree with you if there was a lot of noise, where there's like 500 completely unknown suggestions, and among them are people like this. However, it is almost as if it's the opposite: Given a pool of suggestions that have no mutual friends, the vast majority of them are people I'm at least familiar with, and whom I can't believe have much connections besides a few brief conversations 10+ years ago.



  • @the_quiet_one said in Facebook's Scary "Find a Friend" Algorithm:

    This time the theory of my email being on her contacts list is moot because we only spoke over the phone and maybe via text.

    Text = smartphone = contacts sync'ed to Google (Apple, whatever) = email account.

    It is probably safe to assume that, as far as this feature is concerned, having exchanged texts messages is the same to Facebook as having exchanged some emails.



  • @remi it's even simpler in this case. Facebook app has access to everything on the phone - all contacts, all texts, entire call history, and many other scary things. If this happened within last 8 years, you can be 99% sure Facebook knows your exact relationship.


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