Rights Clash on YouTube, and Videos Vanish - NYTimes.com:
"Countless other amateurs have been ensnared in a dispute between Warner Music and YouTub... The conflict centers on how much Warner should be paid for the use of its copyrighted works — its music videos — but has grown to include other material produced by amateurs that may also run afoul of copyright law.
“Thousands of videos disappeared,” said Fred von Lohmann, staff lawyer for the Electronic Frontier Foundation, an Internet civil liberties group that asked affected YouTube users to contact it. “Either they turned off the audio, or they pulled the video.”A spokesman for Warner Music said that YouTube’s system for identifying copyrighted material does not distinguish between professionally made music videos and amateur material that may include copyrighted works. "