As all users of YouTube know, you can find there excerpts from movies, TV shows, musical performances, and just about anything else you could possibly want to see. Users are free to post videos to the site, and, unless the content is objectionable (or unless the owner of a copyright objects), the videos will remain there.
Viacom recently filed suit against Google (from which, obviously, one can find YouTube) and YouTube for copyright infringement. Viacom contends that these sites should be enjoined from showing Viacom's copyrighted materials. Viacom also seeks substantial damages.
As the attached article indicates, Google is evidently in the process of installing a filter to prevent copyrighted works from appearing on YouTube. Also discussed is whether YouTube qualifies for safe harbor protection as a "service provider."
http://www.mediaweek.com/mw/current/article_display.jsp?vnu_content_id=1003577917