There is no anonymity with bittorrent, your identified by your IP while your connected to the tracker and some clients can log all the connections that are made. I don't know what capabilities the tracker itself has but it's probably very similar in terms of what data about you it can collect. I think a good analogy is if your speeding in your car with a giant neon sign with your licence plate and driver licence numbers. Fortunately, nobody really cares right now but it would not be hard to track if they wanted to. Right now, the RIAA and MPAA are going after the torrent sites themselves and shutting them down but I'm sure they will eventually go after individual users as well.

I'm surprised there actually isn't more pushback against this from the ISP's themselves. If you consider that most homes only use their internet connection a few hours a day and barely use their full bandwidth even then, someone who's constantly using BT would be using probably 75% to 100% of their upstream connection all the time. They have to be noticing that?