Amazon's initial shareholder letters were basically "Yes, we know we're not turning a profit right now, but that's because we believe in our long term plan". They also detailed what they were doing to make sure that their short-term spending was going to result in long-term returns. Amazon's letters and SEC filings were focused almost completely on this message: That we're spending money now to make a LOT more money in the future.

Facebook, perhaps due to the competitive space that they're in, really haven't done anything like that. Their filings have more of a "Deer in the Headlights" feeling than anything else, with mobile revenue being basically 0, and not adequately explaining the massive expense increases for Q2 2012. Those are red flags for investors. It's a completely different message from Amazon's.