Read my comment again, that's more or less exactly what I said. Except I do not see such a simple black and white picture. Taxi monopolies have formed to enable the drivers a better bargaining position. Uber is achieving lower prices by destroying this, and as we can see, once that is done, nothing stops them from turning the tables and driving the price too low for the drivers to survive. The drivers are not their employees, and so not their responsibility. That is the core of their model. I think they're a little more disruptive than needed, basically :)

Taxi monopolies easily grow into a problem. They overprice the rides and stifle the market. But this can usually be sorted out through political action, through opening competition, all without automatically destroying all semblance of security for the workers.