And btw how are we defining Atheist and Agnostic here?
As far as I'm aware, there are solid definitions for these terms, at least as they apply to the discussion here:
THEISM = The belief in a god or gods, or some form of supernatural force of creation.
ATHEISM = The lack of a belief in whatever god or gods are purported to exist.
GNOSTIC = You think you know whether there is a god or gods, or at least you believe it is possible to have knowledge about the "truth" of these entities.
AGNOSTIC = You don't claim to have knowledge of the absolute truth of a god or gods, or don't think it's possible to know with the current evidence.
I would wager most religious people (theists) are also gnostic, since most organized religions are centered around a holy book of some type which claims aboslute knowledge of a god figure who manifested in some way on Earth and relayed information to humanity directly.
Theists can also be agnostic, if they believe in a god and follow its teachings, but don't claim to know absolutely that it is true.
Atheists can also be gnostic or agnostic, and I'd wager that most people erroneously assume that all atheists are gnostic -- that is, that atheists believe that there is no god. Remember, there is a difference between "not holding a belief in a god" and "believing there is no god."
Most honest atheists would probably have to be, in the technical sense, agnostic. This is purely because you cannot possibly know everything about everything in the entire universe, and know absolutely that there is not, nor was there ever, a god. But when you consider that the same uncertainty can be held for unicorns, flying spaghetti monsters, goblins, etc., that uncertainty becomes trivial and useless in discussion and everyday life.
Another very important thing to remember is that atheism cannot exist in a vacuum. Atheism is simply a response to a claim. Whatever the supernatural or god-related claim says, an "atheist" response is that such a claim is either unfounded or lacking in sufficient evidence so as to justify belief.
Atheism also doesn't have to be a wide-sweeping, objective blanket for all claims. We are all atheists with regards to some gods out there. How many people believe in Thor or Zeus? If you don't believe in those gods, then in some sense, you are an atheist.