What happens when you're chillin' on the street, and your arch nemesis has hacked your favorite coffeeshop's PoS system, nabbing your account details, phone identifier, and photo, and proceeds to stalk you all over town from a distance of 100 feet?
The special sauce here is the location tracking. The system seems to assume that vendors are at a fixed location, but there's probably no reason a mobile device couldn't be constructed that functions as a PoS, and with hacked data/credentials, it could be used for tracking purposes. Say, with a number of confederates (or a good make-up job), charging stuff to your account while you're in the area. Or insert intelligence, criminal, stalker, jealous ex, etc., scenarios.
I'm increasingly in favor of cold hard cash for transactions rather than divulging my personal information in ever increasing amounts and rates.