As many here know I worked in the hotel industry for a period of time.

Just about every hotel (in N. America anyways) uses those key cards now. They are a constant source of problems. People's reactions that I've experienced are anywhere from "infuriated" to "couldn't care less." It just depends on the situation. The problem is that those keys get demagnetized very easily. For example if you slip them in with your credit cards.

I can tell you that where I worked, if a front desk agent gave a guest keys to an occupied room, they were immediately suspended. And repeat mistakes were grounds for automatic dismissal! Very serious safety, insurance, and legal issues are at stake, and the hotel stands to lose BIG TIME if they are sued.

I have had this happen to me, and I wouldn't stop staying at a hotel because of it, but I'm not the average hotel guest.
Let me know if you have further questions.

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"I just wanna wish you good luck, we're all counting on you"
-Dr. Rumack