Not Famous?
The time lines are interesting here. The judge was not pointing out that he didn't know what facebook was or how famous it was, he appeared to be pointing at the fact that very few poeple on the planet would have heard of it at the point the www.face-book.com was registered. That was only months after thefacebook website was launched and at the time is was only for students at Harvard.
The registration would have been quite clearly in bad faith if it had been made 12 months later for example, by which time most schools and colleges in the US and UK were participants.