I think a 'cleaner blacklist' would be more useful, but again the legal implications would make it near on impossible. It would be great to have a database of people in your area who have been sacked for being useless, lazy, thieving untrustworthy morons.
On the whole cleaners are an amazingly honest bunch and in all the years of running a company have only had 3 issues of theft, no doubt they got a another job instantly working for another cleaning co and did the same again
.