Facebook certainly has been more diligent about stomping out fake accounts than most other services, with Twitter being social media's problem child.

A telling anecdote: A security researcher friend of mine found a somewhat small botnet of twitter accounts (~7000). Reported it to twitter, a few months passed and he noticed twitter hadn't done anything. So he turned it over to a journalist who eventually poked someone at twitter and... poof all 7000+ accounts were gone 6 hours later.