Welcome to the information age. Facebook has orders of magnitude more information about nearly everyone than those companies. There's no predicting how much they can profit from it yet. Facebook's valuation represents that unknown upside combined with an upward trajectory.
The valuation may or may not turn out to be overly high right now, but it's by no means insane.
The valuation may or may not turn out to be overly high right now, but it's by no means insane.