When taxi drivers find themselves alone in their cabs -- as they often do -- with psychopaths, scam artists, or even just garden-variety drunken idiots, that little hands-free device can be a lifeline.
When you swipe your card, the driver has to pay a hefty 5% extra. Why are New York's cabbies paying so much? Because of all the middlemen. A few people are making truckloads of money on drivers' backs.