Viacom is—as one might expect—the fiercest US defender of its video content on Youtube. The media conglomerate, broadcaster of shows such as Jon Stewart's Daily Show and The Colbert Report, is suing the web video service's owner, Google, for massive copyright infringement; Viacom has had 352 videos taken down for copyright violations, according to MIT's Youtomb project. The Church of Scientology has used Youtube's takedown provisions to stop critics disseminating and mocking its promotional videos, but Tom Cruise's sect is a relatively modest censor—only 48th on our list.