I'm glad to see this clarified. I usually refer to myself as an atheist, but technically I am an agnostic atheist. I think that the problem with these words is that the average person does not appreciate the technical definitions. There are colloquial uses of the labels which imply something different.

To most people, atheists are people who believe that no god exists. Agnostics are seen as a less arrogant breed who claim "I just don't know." Because of this reality, I find it counterproductive to call myself an atheist with people who aren't aware of the distinction. I don't blame people for not grasping the difference, but it does lead to confusion.

The reality is that all 'atheism' asserts is a rejection of deities put forward by other religions. It is a rejection of a claim and technically asserts nothing. Most thoughtful 'nonreligious' people recognize that it is impossible to prove a negative, so a claim that no god exists is impossible.