Those who insist that there is absolutely no possibility of there being a god or any supernatural entity are, to me, guilty of the same kind of conceit as those who claim that a male God created the universe in six days and rested on the seventh: we barely understand our own planet, so who are any of us to say with 100% surety what is or isn't true in the universe? Nevertheless, though I identify as an agnostic, I'd tend towards atheism if pushed (though I'd bet that has a lot to do with growing up UU in Texas).

Here's what matters: I would never want to worship a god who would send a bad believer to heaven over a good skeptic (which is the evangelical party line). When you get right down to it, most religions have at their basis the philosophy of being kind to others and thankful for what's good in life. Why doesn't God exist? Because he doesn't need to. We could do just fine on our own, if we didn't create a need for him.