I don't think it's a problem of not learning the lesson. The problem is that you can't succeed in making a social network if you ask anyone to pay in any way. You need it to be useful, which means you need everyone on it, and everyone won't be on it if it costs anything or is otherwise gated behind even the smallest of hurdles. So rich VCs come in and say, "here's $100,000,000 to go make this thing invaluable, and then I want my money back with a handsome profit". Everyone in the game always knows that the product is going to get shitty when it comes time to pay the piper. Being shitty is a side-effect of making money. The gamble is that it'll be so ingrained in people's life than they'll begrudging eat the shit to keep using it. They're looking for the elbow in the curve -- how shitty can it be before everyone abandons it. That spot of maximum shittiness isn't a mistake -- it's the target.