I've seen fees for failure to return some of the high tech keycards that presumably are a lot more expensive than the normal little piece of this plastic used in most USA hotels.

Unfortunately, I've also stayed in cheap little hotels in Europe that seem to have one permanent key card for each room, often with the room number printed on the card. There's no indication that the key card code is changed between guests or even that the hotel has the capacity to make these key cards.