I think this is a really good breakdown (also in from thisweekmeta, hi!)

The one thing I think you didn't cover as much, though you did reference it, was how amazing an affirming being in one of those filter bubbles feels when you're part of the in group. You're so smart, and so cool and all your friends are smart and cool and everything is ON all the time. Especially if everything's happening at the speed of tumblr. So the incentive not to lose the group (which you talked about) is really high. A lot of isolated teens have never been part of a group that's that strong and feels that fun.