This is easily circumvented...

... by putting the video or audio file in a zip/rar container with a text file, such as the infamous "demonoid.txt" file that comes with so many torrents. Change just one character in this text file and the torrent hash changes. Pirates will simply upload a dozen versions of each movies with a slightly different text file with each, and the overhead from tracking and storing all that hash data will quickly become unsustainable.