I'm not sure that makes sense for regular torrents (e.g. linux distros, large audio software packages, WoW updates, Adobe downloader, etc. etc.) even if it would be a nice-to-have for folks who use torrents for less than legal purposes. And as such, probably not something they can put in without it basically being a signal that they're "helping piracy" (something bittorrent has had to fight an uphill battle for already... I doubt they want to redo that fight)