YouTube
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.

Q: How many copyright infringements must an account have before the account is deleted?
Three