My father was famously a preacher turned agnostic. We used to argue all the time about the difference between an agnostic and an athiest. I felt the difference was inconsequential, he felt it was important. And I've had the same argument with other proclaimed agnostics. I found an amusing way to sum up my view of it in one answer.

What is the difference between an atheist and an agnostic?

The difference is the atheist says she's an atheist, while the agnostic says she's an agnostic.