Interesting paper: "Challenges and Directions for Monitoring P2P File Sharing Networks or Why My Printer Received a DMCA Takedown Notice":

Abstract -- We reverse engineer copyright enforcement in the popular BitTorrent file sharing network and find that a common approach for identifying infringing users is not conclusive. We describe simple techniques for implicating arbitrary network endpoints in illegal content sharing and demonstrate the effectiveness of these techniques experimentally, attracting real DMCA complaints for nonsense devices, e.g., IP printers and a wireless access point. We then step back and evaluate the challenges and possible future directions for pervasive monitoring in P2P file sharing networks.

Webpage on the research.