I almost wonder if there's going to be a "liked it before it was cool" paradox to a lot of these social sharing startups dreams of continued user growth and eventual profitability. Facebook seems to have reached escape velocity as a quasi public utility, a ubiquitous enough communication medium that almost everyone is peer pressured into using it even though they increasing dislike it.

But the other social sharing platforms then become escape hatches for the cool kids to hang out and share stuff in more authentic/novel/exclusive communities, fueling a few to rocket growth and unicorn valuations. But like that indie band you discovered that's now playing on the radio every damn day, the bigger it gets the more the early adopters will move on to something else. And especially in a situation where your primary market is teenagers, there's nothing less cool than what was cool 5 years ago.