I wonder what the credit card ownership rate is in China

Quite small. But everyone has a government-issued ID card, with a unique number. Except foreigners, most of whom complain about people telling them that their passport isn't an acceptable ID (at places like internet cafes, where registration is required for obvious reasons).

By "ownership", do you mean "issued to owner by bank" or "acquired off the black market"?

So, when a legitimate customer doesn't pay attention to that rule, turn away business?

If you're a restaurant who doesn't want your reservations system gamed with, yes.

Scalping reservations isn't innovative, it isn't clever. It's just plain old douchebaggery. Don't be a dick, and its not a problem.

EDIT: With regards to bringing the right card, concerts and other businesses that sell tickets online with a will call option require the same card in person that you purchased with online. I don't believe it to be a burdensome requirement.

EDIT 2: @jack-r-abbit: Okay, how about requiring an Apple ID to make the appointment? And limiting the amount of appointments you can make online? Low hassle yet still effective.

That is a known procedure when buying something online and picking it up in person. And it is somewhat burdensome for people without credit cards. But then those people wouldn't be buying stuff on line anyway. But the Genius Bar is a service that doesn't cost anything and might not even end with you paying anything. And even if you do end up paying/buying... Apple stores still take cash right? Requiring that you give them a credit card just to talk with someone does not sound like the Apple way.

EDIT (to answer the above EDIT 2): Both would be effective and easy for Apple to do if they cared. Although, requiring an Apple ID could be problematic for a person who doesn't have one, right? Admittedly, I'm not an Apple consumer myself so I don't really know what is involved in getting an Apple ID or why a non-user would need a Genius Bar appointment.

I meant, a legitimate customer -- one who has no link to scalpers -- might forget to bring the proper credit card.