Check out this interview with Bittorrent CTO Eric Klinker from Beet.tv. The interview was supposed to be about Bittorrent’s cooperation with Comcast but, as the interview was recorded on Earth Day, the interviewer asked about the environmental impact of P2P.
It turns out Klinker thinks torrents are very green and the fact that the P2P technology makes use of end user's PCs reduces the need for power hungry servers. Have a look at the video below and make up your own mind – I’m not sure that having your computer continuously switched on so you can leech and seed torrents is particularly green, but Klinker puts a pretty good spin on it.