I've worked in a number of hotels and frankly none of the keycard readers/coders had the ability to do anything more than to store the door code and the expiration date. Besides, as was indicated in the Snopes page, the hotel clerks already have access to your address and credit card info, so what would be the point of going to all the trouble of adding it to the keycard? Even the most sophisticated readers/coders I've used in hotels - even the ones that were connected directly to the computers - weren't putting anything "extra" on the cards. If someone really wanted your credit cards or info there are countless better ways to get it. For instance, recently, in Dallas, there was a problem in some of the local restaurants. Some of the wait staff were surreptitiously using small, pocketable scanners (called "skimmers") to steal the customers' credit card info before ringing the sales. They would store lots of numbers each shift and then the info was used to create counterfeit credit cards. So sure, go ahead and keep the keycards and destroy 'em if it'll make you feel better; but there are many other things about which you should probably be more concerned.