Perhaps atheism is ... because some people cannot deal with the idea that maybe they are not the most important thing in the universe
xunker, you are confusing atheism with solipsism. Atheism does not necessarily imply any exalted belief in yourself as light of the universe.
In fact, one may begin with the perception that the physical universe is all that exists, and that entire universe is nothing but matter and energy, moving under deterministic and probabilistic physical laws, devoid of any intrinsic meaning or purpose.
From there one may come to the conclusions that not only there is no divinity or spirituality in any of it, but that you yourself are nothing but a pile of atoms moving under those selfsame laws, and that the self and ego are delusions.
In short, grim atheism is not usually a crutch for the weak, it can be the discarding of an easy illusion, that which you want to exist but really isn't supported by any evidence, and this I assure you is not an egotistical act; living without the illusion of a safety net on the ego.
Jaez's writeup is for the most part excellent, but I disagree with the assertion that An atheist ... would deny belief in Him, even if shown proof he existed.
I think that the belief that there is no God is entirely compatible with a measure of open-mindedness. It is possible to have an opinion - even a strong one - based on the evidence at hand, and to also be able to accept new facts. Of course, an atheistic world-view does not regard most of the so-called evidence for God (e.g. "This book says so", "I really felt the presence of God", "Flowers are pretty", "I have faith" and "It would suck if there was no God") as anything of the sort.
The essential nature of atheism is denial
However, if you are an atheist, try to define your views in terms of what you are for, rather than what you are against. Saying "this is what I'm not" can only get you so far.
Because writeup does occasionally mean reply