You Tube and The Issue of Copyright

YouTube has been criticized for failing to ensure that its videos respect the law of copyright. At the time of uploading a video, YouTube users are always shown a screen with the following message:

Do not upload any TV shows, music videos, music concerts or commercials without permission unless they consist entirely of content you created yourself. The Copyright Tips page and the Community Guidelines can help you determine whether your video infringes someone else's copyright.

Despite this advice, there are still many unauthorized clips from television shows, films and music videos on YouTube. YouTube does not view videos before they are posted online, and it is left to copyright holders to issue a takedown notice under the terms of the Digital Millennium Copyright Act. Organizations including Viacom, Mediaset and the English Premier League have filed lawsuits against YouTube, claiming that it has done too little to prevent the uploading of copyrighted material. Viacom, demanding US$1 billion in damages, said that it had found more than 150,000 unauthorized clips of its material on YouTube that had been viewed "an astounding 1.5 billion times". YouTube responded by stating that it "goes far beyond its legal obligations in assisting content owners to protect their works". Since Viacom filed its lawsuit, YouTube has introduced a system called Video ID, which checks uploaded videos against a database of copyrighted content with the aim of reducing violations.
In August 2008, a U.S. court ruled in Lenz v. Universal Music Corp. that copyright holders cannot order the removal of an online file without first determining whether the posting reflected fair use of the material. The case involved Stephanie Lenz from Gallitzin, Pennsylvania, who had made a home video of her 13-month-old son dancing to Prince's song "Let's Go Crazy" and posted the 29-second video on YouTube.

Source: Wikipedia