The firm, which recently raised $30 million in new capital, has now launched in New York City. Uber, another app, is available in 30 cities and regions, from Amsterdam and Atlanta to Vancouver and Washington, DC.

Uber certainly has changed the cab service in my hometown of Washington, DC. For decades, it was all but impossible to get taxis to go to or from certain parts of the capital city—and harder if you were a minority. Uber, which is based on a smartphone app, changed all that. Uber users fill in their credit-card information and then tell the app where they want to be picked up. Nearby drivers are alerted and one of them will claim the job. The user then gets an estimate of how long it will take for the car to arrive, and can track the driver's progress on the smartphone app. If the user doesn't cancel the car request in a few minutes, a deposit is charged to her credit card.