Supposedly there is a new system out to combat camcorder piracy in movie theaters that uses a technique called spread-spectrum audio watermarking. According to the linked article, the system can precisely pinpoint where a pirate was sitting within a foot and a half.

The system is based on spread-spectrum audio watermarking for the multichannel movie soundtrack. It utilizes a stochastic model of the detection strength, which is calculated in the watermark detection process. Our experimental results show that the system estimates recording positions in an actual theater with a mean estimation error of 0.44 m.

Unless I read this wrong, they would need to find a movie on net that has been pirated. Then analyze the movie and "bingo" they know where the guy was sitting two days/weeks/months ago when he pirated the movie? Call me a skeptic but I don’t think the pirate will still be in that seat when the cops get there.