Much worse is finding yourself behind a customer who needs to present multiple cards at the register to find one that "works."  Just two weeks ago I was at a Long's checkout line and had to wait a looong few minutes while the customer in front fumbled with one "DENIED" card after another.  (I believe it was the fifth card that was the charm.)  No, a perfect world is not where we live.  And also no, such incidents are far from rare.