Your phone has GPS. To be matched at all, Uber had to know both the driver and you, with some mixture of identification/credit/payment information. They relayed your request to just one specific driver, for a pick-up in a specific location. Even if the driver immediately cancels and goes rogue, that's a better record of your-last-known-contact than any other transport system.

Uber relays to you a photo of the driver and the make/color/license-plate of their car – so anyone who pays a little attention won't get in any unvetted cars. The driver gets your chosen alias as another lightweight mutual authentication step – when they call you by that name, they've proven they're in the system.

Taxis still offer none of this. The only check before getting in is, "does it look like a city taxi?" Only flimsy pieces of paper, stuck inside the vehicle, tell anything more about the driver. Turns out, these paint-job and paperwork signals-of-authenticity have historically been easy to fake: http://missionlocal.org/2009/05/mta-poised-to-crack-down-on-...