I remember MySpace ended up blocking YouTube from their site. And YouTube, a small startup at the time, turned to their users to plead to MySpace to activate them again. A few weeks later, they were back in business. But it's interesting to know how close YouTube was to hitting the deadpool.

Edit: Dug up an older article about it: http://www.blogherald.com/2005/12/22/myspace-users-angry-ove...