Mystery Shopper.
I once knew a chap who had some trick cards printed up. They looked very authentic and bore the wording to the effect. "You have today been assessed by Service Authentications Ltd., on behalf of your organisation. A full report will be issued in due course." Or some such wording. They had logos of major companies, BP, M&S, hotel chains etc., possibly even airlines. He would hand a card to a staff member or simply leave one in a place to be found. He amused himself greatly by the distribution of these cards and who knows? He may even have done some good! All highly illegal all the same for the unauthorised use of the logos, but he was never caught or challenged.