A Head Full of Ideas that were Driving Me Insane....

Man, I have the same feeling looking at that picture as I do when I hear about someone getting their bike stolen when they didn't lock it. There's a difference between trusting and just plain dumb.

Until I read further, I thought taking the credit card and then giving it to the front desk was a great idea- enough to inspire panic in the guy so that he won't do it again. But yeah, your next idea is a lot more mature, plus it benefits everyone who sees the warning, rather than just one dumbass.