Adrian Hayter at The Atheist Blogger:
When anything comes up about atheism, Bill Maher reacts in the same way, by claiming that atheists are people who “are certain there is no God”. This portrays atheists in a negative light, because there are very few people who actually would agree with this definition. An atheist is not someone who makes a statement about God’s non-existence, but one who makes a statement about their disbelief/lack of belief/non-belief in God.
[. . .] As an agnostic atheist myself, I’m not against agnosticism at all, and I think Bill Maher is doing a great job making people question the “unquestionable” beliefs of religion. However, he should realise that agnosticism and atheism are not views on the same thing. Following a view of “I don’t know” is fine, but if the question is “Do you believe in God?” and you do not, then you are an atheist.
The only problem is what is the definition of “God” and for that matter “believe?” What To Do About Bill Maher – The Atheist Blogger