When traveling and staying at a hotel with those credit card like keys, take the "key" with you when you leave. Most hotels have your information linked to the keys
This is a common belief, but it is not true in most cases:
http://www.snopes.com/crime/warnings/hotelkey.asp
...though it can happen infrequently, generally with older systems, and more likely outside the US:
http://www.consumeraffairs.com/news04/2006/10/travel_hotel_keys.html
The risk in a hotel key is much much lower than it would be with any individual who might handle your credit card---waitstaff in a restaurant, bartenders, front desk staff, etc. In most hotels (including WDW), the information is "linked" to the key, but not *on* the key, it is generally stored in the hotel's IT system---anyone who could get at the information given the key could also get at it without the key. However, one good reason for keeping your KTTW cards is that they might be valid for charging even after you check out, and those charges will end up on your folio, charged to your account.
But, again, as long as it is a credit card (*not* a debit card), the risk to you is negligible as long as you are paying attention to your monthly statements. Debit cards, on the other hand, are much riskier, because the money is removed from your account directly---usually the bank will make good on their end, but the legal protections to the consumer are much weaker.
http://www.pirg.org/consumer/banks/debit/debitcards1.htm
My wife was once the victim of identity theft---her financial information was obtained from a former landlord by the landlord's son and girlfriend; the landlord had improperly retained the credit check that she ran. It was a hassle, but not a huge one, and it only required some time, no money was at risk. We put a freeze on her credit rating at all three agencies for a while, but eventually lifted it after several years.
. Now if it's something new, that's different.
