Priority: Low at the moment (January 2008). It may become a useful measure if vandal bots or nonsense bots start getting around the CAPTCHA.
See Wikipedia:Project:Protected deleted pages. This functionality appears not to be available in Appropedia's installation of MediaWiki, but is available in Wikipedia.
This page was planned to be used temporarily as a redirect target for protected pages that were previously the repeated targets of spam, and which are not valid page titles. (See Special:Whatlinkshere/Appropedia:Protected deleted pages.) By creating them as redirects they can be soft-protected. However, with CAPTCHA now implemented on all anon edits, this should be less of an issue.