FB is a unique niche. There are in a class all their own in social networking. Down days are good time to add a bit more. If you don't think this is a good buy in the 20's, then go buy AMZN in the 250's. I think we will see this much higher next year.
Though Amazon is overvalued by most metrics, at least it serves a viable purpose to a lot of people. They can buy anything under the sun cheaply. I've yet to determine exactly what purpose Facebook serves, except a personalized version of the National Enquirer.