Facebook has pretty accurate data on 1 billion people. They have not even scratched the surface of how they can monetize it. Think about the equivalent of Google Adsense, syndicated across the entire world wide web, but targetable by detailed and fairly accurate demographic and psychographic profiles. Now layer in the social elements to help marketeres "earn" impressions.

There is a fairly strong chance they will own an enormous % of market share of ALL online and mobile display advertising in the near future.