i mean with public p2p filesharing, you can always "spy" on the sharers. i mean it has the be decryptable for you to download it, right? and youll know who sent it.
and with stuff that hosted somewhere, whether it's some usenet provider or megaupload, you can always shut down the hoster.
people could still pirate by directly sending each other encrypted files, but you'd always have to know someone personally who has what you want. which would make piracy much harder.
why am i wrong? ;)