Originally Posted by
mikesyr18
I did mean in the future, after the purchase has already been made. One could just make a mental note to not visit that certain Subway or that particular Kroger again.
That's fair, but I'd argue that allowed credit card flavors is pretty low or nonexistent on the priority list for most people when deciding where to buy something, especially if you consider that the places that don't take Amex tend to be smaller, local businesses vs. big chains. Product quality, location, hours, convenience, service, etc....
My dry cleaner and favorite restaurant both don't take Amex. I know this and will continue going to them anyway, because I care more about the quality of their product than collecting a few hundred Amex points. If those merchants decide they will start taking Amex as a result of the lower interchange fee, I will continue going there but I will start using my Amex instead of Visa. In that instance, Amex has won those transactions away from Visa.
Perhaps I'm the only one like this, but speaking for myself, I don't factor CC acceptance into my choices of merchants in any way whatsoever. But if more of the places I already spend money begin taking Amex, I will naturally use my Amex more and my Visa less.