I saw this type of statement a lot by Facebook doubters (it could never make money, it would never have real sales, it had no business model, etc).

Let me check Facebook's last fiscal year.

$12.4 billion sales; $2.9 billion profit

Could Pinterest reach $5 billion in sales and $1 billion in net income based on what they're capable of in the next five or six years when it comes to traffic and the obvious monetization? Yes, and it would make the present valuation dirt cheap.

Twitter just turned on their revenue machine two years ago, and they're already at $500m a quarter. They too supposedly had questionable business potential.