I remember reading this great post by Ruby Pseudo late last year and thinking it was a great way to understand social media in general (as well as teens specifically).
One of my favourite of the ten commandments is this:
10. Finally, with Facebook and MySpace etc, please remember that you’re in their (digital) space: they didn’t ask you to be there, and they can’t very well ask you to leave, so talk nicely. And if you haven’t got anything nice to say, don’t say anything at all …
Interestingly, “if you haven’t got anything nice to say, don’t say anything at all” sounds like something my Grandma used to say. I have a feeling she would have gotten on well in the social media world.