Salon.com has a fairly lengthy article up talking about Gnutella. Gnutella is the Napster-esque file sharing program originally developed as an open-source project by Justin Frankel of Winamp fame. It's been championed as being impervious to being shutdown by "The Man" (and in the words of Nat X, I think we all know who The Man is) due to its lack of a centralized server.
Some Gnutella proponents aren't concerned with the fate of Napster, because Gnutella would rise up to take its place. The Salon article points out several reasons why that might not be the case; among them the all-important fact that a recent study revealed that 314 hosts were serving a majority of the files for over 31,000 others. In other words, very few Gnutella users seem willing to play nice and share. If the trend continues, it could make Gnutella worthless.
The article details other hurdles that Gnutella may face, and also provides a history of how the program came about, for those that want to catch up. If you're interested in Gnutella, Napster or MP3's in general, it's definitely worth a read.