One more thing.. people often underestimate the importance of adding smileys or even 'lol' to a post though, as words can easily be misunderstood if you're assuming someone isn't laughing when he was in fact laughing or vice versa.

It has little to do with childish behavior, but more with clarity... Same rules apply as in real life, some one who's smileys 24/7 can't be taken seriously nor trusted, same goes for chat conversations or comments on a forum.