A recent courtcase resulted in an undisclosed settlement (Google paid $millions to copyright holders). From wikipedia:
// At the time of uploading a video, YouTube users are shown a message asking them not to violate copyright laws. Despite this advice, there are still many unauthorized clips of copyrighted material on YouTube. YouTube does not view videos before they are posted online, and it is left to copyright holders to issue a DMCA takedown notice pursuant to the terms of the Online Copyright Infringement Liability Limitation Act. Three successful complaints for copyright infringement against a user account will result in the account and all of its uploaded videos being deleted.
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 $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".
During the same court battle, Viacom won a court ruling requiring YouTube to hand over 12 terabytes of data detailing the viewing habits of every user who has watched videos on the site. The decision was criticized by the Electronic Frontier Foundation, which called the court ruling "a setback to privacy rights". In June 2010, Viacom's lawsuit against Google was rejected in a summary judgment, with U.S. federal Judge Louis L. Stanton stating that Google was protected by provisions of the Digital Millennium Copyright Act. Viacom announced its intention to appeal the ruling.
On April 5, 2012, the United States Court of Appeals for the Second Circuit reinstated the case, allowing Viacom's lawsuit against Google to be heard in court again.[228] On March 18, 2014, the lawsuit was settled after seven years with an undisclosed agreement. //