.com Fan Sites
These are just some of the .com celebrity fan sites. As far as I know, none of these are official, and in most cases don't belong to the celebrity, but if the owner is a true fan and the celebrity decides she wants it some day, the owner will hopefully not make it hard on them.
Legally, as long as the domain is not being used to harm the celebrity in any way, or to make money off the celebrities popularity, the current owner has full rights to the domain. This means in most cases, a fan doesn't have to let the celebrity have it, but a true fan would happily let the celebrity have it.