A recent research paper in the field of P2P technology has been published and considered the “most effective” solution to kill P2P as it is intended nowadays. The research comes indeed with the scary title Proactive Content Poisoning To Prevent Collusive Piracy in P2P File Sharing.
It consists in injecting fake pieces of files to not authorized peers (users who didn’t pay the fee to download) who will never download the complete file, of course (they will download it in infinite time… ok engineers…:) ).
Thing is that the BitTorrent protocol is not affected by this kind of protection since each piece is checked with the SHA1 of the metainfo file (the .torrent file you download from thepiratebay.org…). Moreover all modern BitTorrent clients try to download chunks (parts of a piece for which the SHA1 exists) of the same piece from the same peer. This would prevent a peer to stay anonymous when he will inject a fake chunk. At the first occasion, when the complete piece can be checked, if the checksum fails, that peer is banned from the peerlist.
(Why not informing the tracker with a hey-this-is-a-bad-guy message? I think this can be a protocol extension).

Full paper can be downloaded here.

Another great magic trick of the BitTorrent protocol (although it needs improvements) or just another pompous strategy to prevent filesharing?