"I ought to call myself an agnostic; but, for all practical purposes, I am an atheist." - Bertrand Russell
Atheism, I find, is often misunderstood. To a significant number of people, it is seen as a firm belief that God does not/cannot exist - meaning it's 'just as bad' as religion itself. This is wrong.
Calling Atheism a belief (or 'belief system' as I made the mistake of referring to it in an earlier post, hoping my poorly judged conversational sarcasm would be picked up and my true meaning made clear) is like calling baldness a hairstyle. Again, Atheism is not a belief in the non-existence of God, it is simply a lack of belief that 'he' does.
There is no faith element in Atheism. 'Belief' in certain things from the non-religious is earned when there is a significant amount of evidence to support them - like evolution, or the 'Big Bang'.
Apply this empirical mindset to the God Hypothesis (in it's many forms) and what you're left with is a very easy to define scientific standpoint on the plausibility of the issue; which is that there is no physical evidence for God and we therefore cannot verify 'his' existence... And people interpret this in different ways (and are free to do so, of course).
One way is to declare oneself an Agnostic. Agnosticism - as a stance - concerns knowledge, and some things, it may state, are, despite utilising all possible scientific methods, intrinsically impossible to address. These things, many would say, are not even worth debating. The fence is the adopted position (a reasonable stance in its own right), and Agnostics are likely to neither believe nor 'disbelieve' in God. But this is of course a spectrum, and self-identifying doubters may choose to find the God Hypothesis likely but not certain; unlikely but not impossible; or just not care either way.
Atheists tend to agree with this. The only major difference between the two philosophies, I find, is the interpretation of the inherent unfalsifiable nature of deities, as well as each individual's motivation... (Read more of this post)