said by Dork :
a torrent does not equal the data you get from it. you can simply stop the torrent, or delete the torrent without deleting the data (read crappy movie)
plus if it were deleted forensics could still find a trace
They WANT their work shared so they can sue (or at least threaten to) more later
There are ways around that... The file contents still remain on the hard drive able to be recovered until such a time as the drive sector is over-written. It's a simple matter of re-writing the sector(s) repeatedly to wipe the contents. Once done, no amount of forensics can retrieve the data from the drive.