Channel Hop: The Wiki. First it was hosted on Wikispaces, then after an incident where most of it's content was removed it was briefly put on Wordpress. It didn't last there because the site wasn't free, so they went back to Wikispaces.
It then seemed that they were able to put the lost content back on the Wiki, but yet again they were hit with complaints and the original Wiki was put down for good (a few things being Lost Forever in the process of it all). It was brought back a third time on it's own server.