The clarification of some definitions would help this discussion, because there are two different ways to define atheism. Weak atheism is the lack of belief in a god, and strong atheism is the belief that a god doesn't exist.
A weak atheist lacks belief in a god for the same reason that any rational person lacks belief in unicorns, leprechauns, and flying whales: there is no evidence. Someone who doesn't believe in talking toasters is not required produce a systematic study proving their nonexistence. Similarly, a weak atheist is not required to support his position with any arguments of his own. The most he can do is show that the arguments supporting the existence of a god are flawed. Refuting theistic arguments does not prove the nonexistence of god, but the weak atheist is not attempting to do this anyways.
A strong atheist, on the other hand, must make an argument that a god doesn't exist. There are many different ways to define 'god', so a strong atheist's evidence might only disprove a particular subset of the gods. For example, a god that created each individual species of organisms cannot exist, because it is known that all organisms evololved gradually through an unintelligent process. Someone who is a strong atheist with respect to one god might be a weak atheist with respect to others.
Also, atheism and agnosticism are not mutually exclusive. Agnosticism simply rejects the idea that it can be known whether a god exists or not. There is nothing contradictory about calling oneself 'an agnostic atheist'. Concerning a god that simply created the universe but left no other trace of himself, it would seem logical to adopt the agnostic position.
I see nothing weak about strong or weak atheism.