I think it was in a video with to mscott where woman from twitter talked about this, yes false positives are a big problem when detecting fakes.
But Twitter is working hard to keep bad bots / fake accounts away. There was no last time, right now people are working on banning fakes. It a 24/7 game.
There was a similar discussion last week (or so). It was basically said that even if "the media" does track us, it's still a good thing "they" allow some autors to write about privacy.