I don't think facebook is overvalued. The bubble aspect of the current situation is due to the increased allocation of capital into the tech industry because of big successes such as Facebook, Groupon, LinkedIn, etc. The worry is that this infusion of capital will result in 'bad' companies getting funded.

Considering how many startups are being founded by MBAs these days (MBAs will always follow the money), you have to wonder if they are all really creating something worthy of their sky high valuations.