Stepping back a bit, assuming one can grow a social media platform to XX% of the population, what makes it any more or less valuable than the next fad/platform that grows to the same XX%? If you are selling eyeball-time via ads, the two platforms have similar value. Maybe it's a little bit different with better ad targeting. But any arguments based on "our audience consists of well educated 18-35 year olds with disposable income" lose merit once growth plateaus and you realize that your audience is just the same general population that cable reached 20 years ago.