This solves half (and only half) of the problem that Uber is trying to solve. A feedback/rating system is fantastic if the consumer has choice. Unfortunately, the iPhone app does not have the ability to help consumers choose a taxi driver when they're standing on Broadway at 2 am with their arm in the arm---they're going to take the first cab that shows up no matter how awful it may be.

In fact, the whole idea of the taxi bargain is that you pay a fixed price to get a minimum standard of quality --- enforcing the minimum standard seems likely to be a more productive avenue than increasing the average.

A more direct solution might be an app that submits complaints to the Taxi & Limo Comm'n, since the fear of losing a medallion is far greater motivator to most taxi drivers than the prospect of being named on an awards list. (Again, for Uber and similar systems, reviews do matter to drivers because consumers choose.)