Answer:
QQ are a pair of crying eyes, or in the past, there were games, that if you pressed alt QQ, you would log out. So ppl said: why don't you QQ already noob...
Then started games, like Combat Arms, CSS, MW2 etc...... And that's when the crying eyes started, so when someones says like: YOURE HACKING!!!, a person usually says: No QQ nub\!!!
QQ also means quick question