One recent realization: I suspect many (read: more than just teen girls) see social media as a real-time status market. There is a constant stream of information, and the subtext of that is often status-oriented. Thus, for the status-hungry, keeping up with updates feels necessary even if it makes them feel terrible.

There are elements of addiction at work here, too, but if social media was a net negative it wouldn't be as sticky as it is now. People are obviously getting something they want from it.