LOL drift (as I've somewhat pretentiously named it) is an interesting linguistic phenomenon: the phrase has leapt its bounds as a signifier of its typist actually laughing out loud and become, to some people, an all-purpose humor mark, joke acknowledgement, the yin to :-)'s yang.
This is what the human mind does to symbols, once they become effortless (you can't force a laugh with the ease of pushing three buttons) -- disentagles them from their origins and starts going on functionality alone (though the original evokation, in this case, still isn't swept away by any means; in the first instant your eyes* see the first first sentence of this writeup, before you actually start to read it, it looks oddly cheerful; a bit like hearing a distant laugh and then realizing it's just a bird).
*Or my eyes, at least. Maybe I spend too much time online.