Update 7th June 2010
These are all gone on Stack Overflow and Super User. ServerFault is a different story:
https://serverfault.com/questions/tagged/belongs-on-superuser - 189 questions
https://serverfault.com/questions/tagged/belongs-on-meta - 0 questions
Update 9th June 2010
Stack Overflow links for reference:
Also https://stackoverflow.com/questions/tagged/belongs-on-meta - 0 questions.
Super User links for reference:
https://superuser.com/questions/tagged/belongs-on-meta - 0 questions.
Unfortunately the quick retagging exploit for closed questions no longer works.