Ahead of me might be someone who's desperate to be modern and pay with their Starbucks app. They wave it at the scanner. It doesn't work. They wave it again. It still doesn't work. Then they poke at their phone. They wave it again. Finally a beep. My regular baristas, Kurshina and Marie, have patience coursing through their veins. I, however, mutter through gritted gums: "Wouldn't it have been easier to pay cash?" It seems that such a scenario might have played a part in one of the more spectacular customer service angerfests of the year. This one was at...