How about instead of deleting them they are blocked from crawlers and all links are rel=nofollowed? That way the information is still available to anyone who knows it exists, but it won't show up in searches. I'd be fine if this is done via an overlay site with Wikipedia as the backend, or better yet, like showdead on HN (which I keep enabled, since sometimes an account gets killed for a single post and the other posts are interesting).