@lrucker said:
Wouldn't "There's probably no god" be the agnostic bus?
There are varying levels of atheism. "Strong" atheists assert that there are no gods, as certain undeniable fact. "Weak" atheists assert that there is no proof for any gods, and thus the chance of any existing is very slim, so the assumption that gods do not exist is a good one. Agnostics take that level of uncertainty one further by asserting that there is simply no way to come to a conclusion one way or the other, and thus remain undecided.
Additionally, almost everyone is an atheist in one form or another by denying the existence of various gods. People that identify themselves as atheists just tend to leave out the one god that lots of other people believe in.