FORTUNE -- You need a ride. Instead of lingering at the intersection flailing your hand in the air, you fish out your smartphone. A few taps later, Uber's slick, futuristic logo appears, a seriffed "U" hovering over a stark black background. Signing up takes a few seconds. Once you provide basic contact and credit card information, a Google map pops up displaying your nearby surroundings. You select a spot on the screen to set a rendezvous and watch as a car-shaped icon inches toward it. When a black sedan pulls up a few minutes later, the driver welcomes you by name and offers free snacks and bottled water. At your destination, the fare is automatically charged to your card. No fumbling with wadded cash. No flimsy receipts to stash away. You simply hop out and go.