A technical report ("Challenges and Directions for Monitoring P2P File Sharing Networks—or—Why My Printer Received a DMCA Takedown Notice") by two researchers at the University of Washington's Department of Computer Science and Engineering calls into question the accuracy of media companies' BitTorrent infringement detection methods.
Here's an excerpt from the paper:
Copyright holders utilize inconclusive methods for identifying infringing BitTorrent users. We were able to generate hundreds of DMCA takedown notices for machines under our control at the University of Washington that were not downloading or sharing any content.
Read more about it at "The Inexact Science Behind DMCA Takedown Notices" and "Study Reveals Reckless Anti-Piracy Antics."