Update 7th June 2010

These are all gone on Stack Overflow and Super User. ServerFault is a different story:

http://serverfault.com/questions/tagged/belongs-on-superuser - 189 questions

http://serverfault.com/questions/tagged/belongs-on-stackoverflow - 14 questions

http://serverfault.com/questions/tagged/belongs-on-meta - 0 questions

Update 9th June 2010

Stack Overflow links for reference:

http://stackoverflow.com/questions/tagged/belongs-on-serverfault - 0 questions.

http://stackoverflow.com/questions/tagged/belongs-on-superuser - 0 questions.

Also http://stackoverflow.com/questions/tagged/belongs-on-meta - 0 questions.

Super User links for reference:

http://superuser.com/questions/tagged/belongs-on-serverfault - 0 questions.

http://superuser.com/questions/tagged/belongs-on-stackoverflow - 0 questions

http://superuser.com/questions/tagged/belongs-on-meta - 0 questions.

Unfortunately the quick retagging exploit for closed questions no longer works.