I have noticed the "property of XYZ Casino" on the back of the cards. I would think that the issue on the registered cards is the personal information given the casino to obtain the card in the first place. You could use the obtained card to run up points and then try to cash them in under someone else's name, thus taking their points or comp's, generally you need picture ID. Weak, but maybe the concern. Blank cards would seem like good advertizing but who knows. Take care...and good luck