Facebook may not have started doing everything they're doing now, but they do have it now. Any new competitor is not going to be judged based on what Facebook was 10 years ago; they're going to be judged against it now.
MySpace UI was terrible. You just can't allow regular people to edit CSS of their profiles.
MySpace was like high school, FB was like college. More grown up and sophisticated. Exclusivity was part of it.