I've always seen store returns as an ethical issue. If at the time of purchase I have full information about the product, I see it as unethical to change my mind a few days latter simply because of buyers remorse. One of the examples given in the article mentions the author returned a playstation after playing it for a few days. I don't see how this is a reasonable return, and it cost the store money all because the buyer was fickle.
The main story from the article is a bit different, as the user bought the case expecting X and got Y. I have no problem with returns of this nature. A reasonably informed consumer would not expect there to be two products from the same company, with the same name just only sold at different locations.
I'd probably call up AMEX and cancel the charge.