According to a ruling made by United States District Court Judge Harold Baker, identifying the address assigned to your computer when it's connected to the Internet is not the same thing as identifying the person who's using the computer. Such a precedence spells trouble for copyright holders seeking to subpoena ISPs in order to locate and identify potential copyright violators.
Judge Baker's ruling came as a result of the VPR Internationale v. Does 1-1017 case, where VPR, a Canadian pornography producer, was asking for the right to subpoena ISPs for information concerning suspected copyright infringers, of which, there were 1017 of them. The court's ruling, which is available in its entirety here, not only denies the initial request for an expedited discovery, it also discusses a rejected reconsideration request from March 22, 2011.
That, coupled with the text of Judge Baker's stance, makes it quite clear that recent IP address identification mistakes were a driving force in his decision.
While VPR acknowledged the request fell outside of normal procedures, it was nonetheless compared IP addresses to car rental records. The request continues:
If a plaintiff was injured by a rental car, the plaintiff can discover the information on who leased the car from the agency by specifying the license plate of the offending vehicle and the date and time when the injury occurred. Without access to the agency’s records, all the plaintiff has is the identity of the rental agency, but not who was driving the rental car...
While the rental car comparison may hold some validity, it's not often an unknown entity is catching a piggy-back ride with the rented vehicle, using it to steal other cars without the knowledge of the primary driver/car renter. Judge Baker concurred, saying not only did VPR fail to identify any of the 1017, there's also doubt concerning whether or not IP addresses are accurate methods of identifying the sought after user.
From the ruling:
Carolyn Thompson writes in an MSNBC article of a raid by federal agents on a home that was linked to downloaded child pornography. The identity and location of the subscriber were provided by the ISP. The desktop computer, iPhones, and iPads of the homeowner and his wife were seized in the raid. Federal agents returned the equipment after determining that no one at the home had downloaded the illegal material. Agents eventually traced the downloads to a neighbor who had used multiple IP subscribers’ Wi-Fi connections...
Furthermore, Baker refers to VPR's tactic as a "fishing expedition."
Although this doesn't mean copyright violators are safely hidden behind their IP address, it does mean the burden of identifying suspects falls where it should: At the feet of the accuser. If an accusing entity can't offer anything other than an IP addresses, there's now precedence to throw such requests out.