One of the most annoying occurrences I run across with fellow atheists is the claim that atheism is not a belief, but a lack of belief. To me, this argument seems unimportant and a bit nit-picky. I understand the logic behind it - atheism isn't a belief but rather a lack of belief in a god or gods. Yes, OK. However, since the question of whether there is a god or not is at present an unanswerable one then to not believe in god is still a belief in that you believe that there is not a god. Rearranging the words of the conviction to say "I don't believe in god" doesn't automatically make it less of a belief.
I think the issue that is raised here is the lack of congruency in regard to what constitutes an atheist. Some are ardent and convinced that there is no god. Others are unconcerned with the existence god and simply don't feel that the issue deserves much of any consideration. The latter position begins to bleed into the gray area of agnosticism, but I know plenty of people who feel entirely unconcerned about god but who still consider themselves atheists. I have found that an atheist is an agnostic is a non-believer is a freethinker, all depending on who is considering the source.
The only reason the issue of whether atheism is or is not a belief seems to stem from a habit of religious detractors who like to claim to that because atheism is a belief then atheism must also be a kind of offshoot of religion, requiring the same faith which atheists and anti-theists often ridicule religion for relying on. The problem with this argument is that while the entirety of religious belief is based on faith (if we are to cast aside ridiculous pseudo scientific arguments which we should because they're crap), atheists form their beliefs based on empirical data and scientifically sound evidence. When you consider the difference between the sources of information either opinion is based off of, the argument that atheism is the same kind of belief as belief in god falls apart quickly because it's clearly not.
To touch a bit more on pseudoscience, the very essence of the difference between belief in god and belief that there is no god is what gave birth to the aggravating practice some religious groups have adopted of trying to warp scientific information or at times completely making up science to try to prove their religions as valid. This paired with the insistence that believing there is no god is no more valid than believing there is a god is a kind of religious two pronged attack on atheism on all fronts. If atheism really is a belief in the same respect as religiousness is a belief, there would be no need for pseudoscience to even exist.
I don't see any reason to argue whether atheism is or is not a belief because I feel like it's a moot point. If you say it's a lack of belief or you claim it's what you believe and is therefore your belief, neither position is incorrect or more correct than the other. I feel like the wholehearted rejection of atheism as a belief within the atheist community is almost an indication of cowering to the pressures of the religious who seek to invalidate our position with semantics, pseudoscience, and conflated convictions in regard to belief.