Medium has a helpful guide dissecting teens' taste in social media. It's such a constantly moving target that I don't feel that bad that I've never heard of Yik Yak.
I adore Tumblr, but I'm amused by the description of its "non-judgmental" atmosphere. OK, it's better than most, I guess.
I'd be very interested to get a breakdown like this from a girl's perspective, considering the troubling prevalence of online misogyny, an issue that's not as publicized as it should be.