According to anti-trust law.
Is facebook a company with dominant position?
Anti-trust laws require far more than just being popular to apply and there's nothing in them that applies to Facebook or any other website. Anti-trust laws in the U.S. have never successfully been used against a website because the very notion is absurd.
Yeah, I'm gonna bet on me and my law degree for being right about that. Whether Facebook is in a dominant position is for the court to decide.
You on the other hand are a funny... dude. Haha, "dude" he says :)