Good points. I guess we'll just have to stick with the "charge 1 cent" method.
I'm sure if people really did that, the WTS would want to track down who it was, and send the elders after him/her.
I.e., if they see 100 1 cent transactions from a card belonging to "Fred Herpaderp" made at a circuit assembly on October 1, and they know that Oklahoma Circuit 1 met there that weekend, they could call the Oklahoma 1 CO and ask what congregation Fred belongs to, and then sic the elders on him.
Is it legal for a credit card vendor to use the name on a credit card for such a purpose?