its mainly that recent green paper, about as much use as toilet paper
Scare tactics by the media atm...
think about it, EVERY ISP has to use serious SPI hardware to monitor billions of files per day, and even then BitTorrent would be excluded (and similar) because its "packets" of data, not complete connections with files in, so this would be hard to trace anwyay. each isp would need databases for each customer (see where this is going) ?
I wouldnt worry about it

- most ISPs cant run the service at a reasonable speed without this, if it does get in, maybe it will kill the likes of AOL and Tiscali tho
And most ISPs would need new kit / better training so that they could even define p2p apps by how they "look" rather than by port - (as i think Enta still use port restrictions?) and new services like 4od and BBC iplayer will make things very difficult