Haha or hehe?

Here is an intersting remark. In the world of online chatting on msn or yahoo messangers back home, when someone says something funny and you want to say you're laughing without using an emoticon, you would usually say "haha". But, when I came here I noticed that everyone says "hehe". I wonder what could be the explanation? Could we say that from the cognitive psycholinguistic bilateral dynamic perspective, using "haha" actually encodes the meaning of laughter, and entails that you make more noise when you laugh, while conversationally implicating that you are not afraid of people seeing your teeth when you open your mouth to say "haha"? On the other hand, saying "hehe" could be said to encode the same thing, but entails that you make less noise and conversationally implicates that you are too lazy to open your mouth. :)

Ok, I know, I am loosing it. Reading too much in the past few days messed up my mind. Besides, who cares how you express laughing? After all, 'life is not all haha heehee' :) But wouldn't it be nice if it was? :)

p.s.
there is actually a show on TV called 'life is not all haha heehee', I just saw the posters of course (living a TV-less life, remember?)

Mai