There was actually a thread on reviewing 'mongers in the national suggestions forum a while back. 'Reviews' like the above by UtterNonsense are probably something a lot of 'mongers are afraid of, which is why the idea of reviewing 'mongers generally went over like a lead balloon in that thread.
A referral database wouldn't have to be too much more complicated than Preferred 411's OK system, though as I'd stated in that 'monger review thread, a basic checklist of hygiene/behavior issues or hopefully lack thereof wouldn't be a bad idea and might help ease screening and make things easier for ladies and gentlemen wanting to set up dates.