> Uber is proving that car service is not a natural monopoly. If the dominant provider is taking too many liberties with pricing, someone else will come in to right the market.

This is complete nonsense. Car services have never been a monopoly, natural or otherwise; in every major city there have always been multiple car services. Uber's valuation is premised almost completely on the hope/expectation that they can become a monopoly and start exploiting their market position to the detriment of everyone.

Seriously, check out the Naked Capitalism series linked above. It lays out in great detail why Uber is not in any way an example of someone "coming in to right the market". They're wronging the market.