Two key facts about Twitter and Facebook. 

1. Twitter's mistake was building a product they didn't really use. I've never seen it work out well when the top guys at a company aren't passionate users of their own product. They can be quirky, that just comes out in the product. Gates and Windows. Jobs and the Mac. Marc Andreessen and Netscape. Etc etc. When the people who run Twitter get on stage and talk about their product, it's very different from the thing we're using. You can feel the discomfort. It's distant. It also comes through in the decisions they've made re business models. 

2. Facebook can only rise so far because they're hiring from the same talent pool as all the other Silicon Valley companies. They all think they're going to be different, and for a while they are. Until they grow so big that everything that was different about them gets diluted. Eventually the singular Silicon Valley Company takes over. I remember when Apple was young, their execs were the most wonderful people in the world. Almost as if "wonderful" was a technical term. They were thinking about taking over and running third world countries after their Apple options vested. Seriously (and I'm not making fun of them). But they all fall to earth, and become the foundations and plaster for the next upstart.  

Are we in a bubble? Yes, this is a bubble. All the frenzied startup activity and still the VCs raise more money to invest. Not enough inventory. We need more young people to play the role of entrepreneur. It's so analogous to the real estate bubble where the only bad bet was to own the actual real estate because that was so real. The money was being made off the lies. In this bubble the people who are going to get hurt are the legions of young people. Most of them aren't entrepreneurs. As a percentage of the population, the people who really have the drive and fortitude to stick it out is infinitesmal. But that isn't the myth -- it's also like the housing boom where everyone could be a home owner. In 2011 every young person can be an entrepreneur, esp if he or she knows how to code. That's the bubble, right there.