Talk about a straw-man argument. That's not the OP's situation. What happened was his card was declined. Of course the hotel should have at least had the courtesy to e-mail him and ask him to replace the card or cancel the reservation. Especially for an award reservation. Especially for a Diamond member.

"It was the customer's fault" is not mutually exclusive with "the hotel should have done something out of basic customer service."

If a guest leaves something in his room after checking out, wouldn't reasonable customer service be for the hotel to contact the guest, even though it was the guest's mistake?

If a guest breaks something minor in the room, say a light bulb, wouldn't reasonable customer service be for the hotel to replace it, even though it was the guest's fault?

If a guest trips on his suitcase in the lobby, wouldn't reasonable customer service be for a hotel employee to help him up, even though it was the guest's fault?

Some of the responses here are ridiculous. Hotels are in the service business.