The valuation still doesn't match reality. People seem to forget competition exists and Facebook seems to think they can keep trying to control things, and that people will want to be on their platform long-term. In reality even for businesses the chances of people seeing your content isn't very high - of course one model being that Facebook wants you to pay to increase that exposure. It's just not the best possible structure for businesses, or consumers. Sure, it might be good enough for now, and all that exists in a good enough form for people to use - however I imagine better systems will evolve, and Facebook won't be able to buy them for $1 billion (or ~$300 million + stock, whatever it was).