Just because we are willing to be rational and admit that to be a true atheist you have to KNOW that there is no god. How can we really claim such a thing? I don't think that really qualifies us all as agnostics, though.
I think a lot of religious folks, Christians at least, seem to have god confused with Santa Claus; this compassionate fellow with a white beard who watches over us deciding if we've been naughty or nice....
Do you believe in Santa, or do you hold proof that he doesn't exist?