I got one of those letters from Comcast a few months ago.

The "works" involved in my offense was a movie that had just opened in US theatres and the copy I got was a CAM (recorded by camera in a movie theatre). Either of those two factors are enough to set off alarms with your ISP. I was specifically cited for seeding the video.

I stopped downloading altogether for a month. After that I resumed downloading but I make sure to avoid CAM copies and movies currently playing. I also stop seeding as soon as I have completed the download (unless it's a movie that is a few years old, something that is in the public domain, or things like foreign documentaries). I have not heard anything more from Comcast.

As LotR said, p-p filesharing, and Internet neutrality, will only get worse if we do not question our elected officials and get rid of those who support restrictions. The RIAA and MPAA have a Monsanto mentality.