Selected answers from the Dumb SEO Questions Facebook & G+ community.
Wissam Dandan: The only reason I would recommend that (where I create a dedicated sitemap for these URLs) is when I need faster process of these urls to be removed from search
Alan Bleiweiss: And once that sitemap is processed, it`s important to remove them from the sitemap. Noindex or dead URLs in sitemap files can weaken crawl trust and crawl efficiency.