josephstern, thanks again for sharing. I am fascinated by this sort of behind the curtain info about credit card processing. We swim in credit card transactions and can as little about the out of sight details of them no more than we do about the air we routinely breath, at least if that air is not somehow foul with pollutants. Plastic has become so commonplace that cash often seems strangely old fashioned. I don't know that I have ever seen anyone produce cash at an airline ticket counter, and I think if you do pay for a ticket with cash, you are likely to get special screening when you fly.

None of this will change my plans to pay with my MP Visa as much of my taxes as will bring me double miles and no more. It does, however, help inform me about what is going on. (BTW, no double miles offers from AmEx, especially SPG AmEx, which has had them in the past?)

josephstern, a couple more questions in this vein, if I may - are merchants allowed to set a minimum charge, e.g., $10, below which they will not accept plastic, or does that violate their agreements with Visa, MC, and/or AmEx? Do they get hit with a fixed fee component, making small charges more expensive for them, and thus their cash requirement for small purchases? Do you care to say what sort of business you are in?