I used to bring back keys for a friend that 'collected them'. Thought it was rather odd, but eventually found out that he was really going to places like Vegas, staying at some fleabag hotel & using the 'collection' to flash at the attendant at the better hotels to get access to the pool. He also used it for the the free breakfasts @ the Embassy Suites. Thought that was really cheesy and I never bring back cards anymore.