Reading peoples blogs today at joeuser.com I found out that Sir Peter Maxwell had created a website for disillusioned joueser.com bloggers. I've seen this before at vbforums.com
A group of people don't like the adimistration at the old site. They then create a spinoff site that may or may not be succesfull. In my experince this only happens when you have a site that forms a community of groups of people who like to chat to each other.
When the point of the site is something external to the community these spinoff sites don't seem to form. For the spinoff to be succeful there needs to be a core group of people that chat together. In the non commuinty centered sites you don't get as many or as big of groups that chat together so statically it's less likely that you have a succeful spinoff.