Last modified: 2011-03-13 18:04:40 UTC
Page moves are usually only done within the same namespace. However, recently there was a page-move vandal who moved articles into his own namespace in order to trick admins into deleting them. I see no reason why a user should be able to do such a move. Other than moving an article from a personal sandbox into the main namespace, where there is no reason to preserve the history. In case a cross-namespace move is necessary, an admin should be able to do it.
Sorry, but this makes too many assumptions about the distinctness of namespaces. In sites with multiple content namespaces, it may make perfect sense to move articles back and forth if they're misplaced, and surely there's no particular reason to prevent non-admins from userfying pages that would otherwise be deleted for some reason, for instance. Essays might be moved between project and user space, many moves would be needed if a new namespace is created, all in all this isn't sufficiently distinct from ordinary moves to justify a distinct permission, and certainly not one restricted only to admins.
The answer to move vandals, like to any vandals, is not to make it more difficult for anyone to do anything, but to make it easier to revert them when they do it. That's the idea of a wiki.