Pinterest has a: show me the sales, problem, I suspect. Public comparables in social like Twitter & Snapchat are going to cap their upside until or unless Pinterest can somehow demonstrate a very profitable business model. If those margins never arrive, Pinterest is going to be worth something a lot closer to Yelp than Twitter. From $12 billion, there's a massive downside risk in the last few rounds for Pinterest investors if this gets a similar reality chopping to what Twitter & Snap have.