That is the question. I don’t think it’s a question for atheists as a whole to decide, but is instead one each individual must ask him/herself.
For me, it’s been rather simple: as a general matter of practice, I don’t associate with groups. It’s hard enough just identifying as an atheist for me… I can’t personally imagine gaining anything from surrounding myself with other atheists and counting myself as “one of them.”
I have read Christians and believers in other religions talk about how the most bitter and angry responses often come not from atheists, but from fellow believers. And it’s not just Protestants and Catholics going at each others’ throats; it’s Protestants damning other Protestants, and Catholics condemning other Catholics.
These people are basing their beliefs off the same book and overall dogma, and yet they still can’t get along, so I don’t hold out hope for finding any kinship with other atheists as a whole. Atheists have no common ideology beyond a rejection of gods… oh wait, we don’t even have that.
This is not to say I can’t identify with other atheists, but I am just as able to identify with a Christian or a Buddhist or Odin worshipper (I even had an acquaintance who was a Moonie). If you consider that I am undoubtedly going to differ from someone in some way, it might as well be on a matter as inconsequential as their stance toward the gods.
After all, there are Christians who are pro-abortion socialists. I don’t really care that they agree with me politically for completely different reasons (like, that people should be allowed to sin or that America is a Christian nation, and Christians are called to help their neighbor). For me, it’s all about “what” you believe, not “why” you believe. You can’t fix anything with good intentions, and plenty of good things have been done ruthlessly.
So ultimately, I don’t feel any need to make the precondition for meeting someone the fact that they don’t believe in gods. This is not to say I am not glad there are atheists out there networking and exchanging ideas. There’s no “but,” either. It can only help me if people are working to make life easier for atheists, and I guess part of accomplishing that is forming an organized group. That stuff is just not for me.
For me, part of atheism is not associating myself with other people based on my theological opinions. This isn’t an inherent part of atheism, merely a characteristic I have associated with atheism. That is the nature of atheism: it is what we make of it.
And by “we,” I mean atheists. I see the religious spending a strange amount of time making claims about what atheism is in blogs, lectures and what not. Oddly enough, in all of this pontification, they usually do not even correctly identify the one thing that atheism is (or, at least what it should be, according to its literal meaning).
But why would Christians know? There’s so many atheists out there saying so many things, it’s no wonder the picture of “what atheism is” has become a muddled mess. But I think that is what atheism ought to be: flexible, inclusive, the sort of things a religion is not.