A Wired article today has the bold headline Hollywood Wants BitTorrent Dead.

In the United States and the United Kingdom, the Motion Picture Association of America, the main lobbying arm of U.S. film studios, filed civil lawsuits against more than 100 operators of BitTorrent "tracker" servers that point to locations where digital files of movies, music and other content can be found.

From Wired News: Hollywood Wants BitTorrent Dead
Referenced Wed Dec 15 2004 19:27:05 GMT-0700

BitTorrent is a protocol that can be used to transfer large files. Clients are simultaneously servers so that the originator of a popular file doesn't have to pay the full cost of its distribution. More importantly, the protocol's performance improves as its popularity increases since there are more servers to take up the load. This makes it an important technology for distributing everything from podcasts to Linux ISO images. This analogy might help explain:

One analogy to describe this process might be to visualize a group of people sitting at a table. Each person at the table can both talk and listen to any other person at the table. These people are each trying to get a complete copy of a book. Person A announces that he has pages 1-10, 23, 42-50, and 75. Persons C, D, and E are each missing some of those pages that A has, and so they coordinate such that A gives them each copies of the pages he has that they are missing. Person B then announces that she has pages 11-22, 31-37, and 63-70. Persons A, D, and E tell B they would like some of her pages, so she gives them copies of the pages that she has. The process continues around the table until everyone has announced what they have (and hence what they are missing.) The people at the table coordinate to swap parts of this book until everyone has everything. There is also another person at the table, who we'll call 'S'. This person has a complete copy of the book, and so doesn't need anything sent to him. He responds with pages that no one else in the group has. At first, when everyone has just arrived, they all must talk to him to get their first set of pages. However, the people are smart enough to not all get the same pages from him. After a short while they all have most of the book amongst themselves, even if no one person has the whole thing. In this manner, this one person can share a book that he has with many other people, without having to give a full copy to everyone that's interested. He can instead give out different parts to different people, and they will be able to share it amongst themselves. This person who we've referred to as 'S' is called a seed in the terminology of BitTorrent.

From Brian's BitTorrent FAQ and Guide: What is BitTorrent?
Referenced Wed Dec 15 2004 19:30:47 GMT-0700

If you read the Wired article, you'll see that what the MPAA went after was something called tracker sites.

BitTorrent, eDonkey and Direct Connect allow millions of internet users to share copies of movies, music, software and games. The services don't host the files themselves; instead, they point users to other users who have the files available for sharing. In BitTorrent's case, users tap tracker sites that keep dynamic lists of where files are stored and available for download. The MPAA is trying to cripple BitTorrent and its peers by suing people who host the tracker servers. Because of its efficiency in helping users handle very large files -- such as digital copies of feature-length films -- BitTorrent has attracted the enmity of Hollywood.

From Wired News: Hollywood Wants BitTorrent Dead
Referenced Wed Dec 15 2004 19:38:08 GMT-0700

This makes it sound like tracker sites are analogous to the search server in the old Napster, but that's not really the case. The tracker is similar in that its the only centralized piece in all of this. It serves a different function, however. The tracker is a server that coordinates the trading of the various bits of the file. Trackers do not have any knowledge of the content of the files and aren't used to find the original file. Their limited duties make them fast and able to support large numbers of users with limited bandwidth. Note that unlike Napster, there's not just one tracker. Every file being distributed could, potentially, have its own tracker.

If you read the article without a clear understanding of what a tracker does, its easy to think that the MPAA just went after "the bad guys" and that trackers being used to legally coordinate the distribution of other material could remain untouched. But how can you tell which is which? It would seem to me that someone running a public tracker is in the same position as an ISP or common carrier. They don't know the content and therefore can't be held responsible for it.