There's a nice quote from Jonathan Zittrain in a New York Times article on the "Grey Album" (a re-mix of some Beatles tracks with some recent rap music) dispute:

"As a matter of pure legal doctrine, the Grey Tuesday protest is breaking the law, end of story. But copyright law was written with a particular form of industry in mind. The flourishing of information technology gives amateurs and home-recording artists powerful tools to build and share interesting, transformative, and socially valuable art drawn from pieces of popular culture. There's no place to plug such an important cultural sea change into the current legal regime."