You know, me and my cousin were vid chatting with our webcams, and he didnt have a mic so he used his keyboard to talk. Well, the funny thing is that every time I made a joke (good jokes) he would type "lol" or "hah", but the expression on his face wouldnt change. So really, I found his chat expressions less, well, expressive.
I say that we only write something such as "lol" when we find something genuinely funny, like something that makes us laugh, or at least crack a smile.