I'm not familiar with all the startups mentioned, but I have to say this: I think Pinterest will be a several billion dollar company and either IPO (likely) or get acquired by Amazon (maybe). If I could buy the stock a decent price, I would.

I say this based on (a) my own experience seeing it drive traffic to some recent consumer projects and (b) seeing how every woman in my life (from my 18-year-old daughter to my 62-year-old mother in-law) uses it as a giant shopping list for their lives.