> This rests on the VC assertion that Uber is playing a winner-take-all game.

They certainly seem to be playing a winner-take-all game, by heavily subsidising rides when they first launch in a new city.

But it seems questionable to conclude that taxi services really are a winner-take-all market. Many Uber drivers I see have multiple phones, running multiple taxi apps at the same time. And most people I know have at least two apps in their phone. I usually check three (Uber, an European one, and a local one in my city) before making an order.

There are some network effects to taxi services - customers want a car fast, and drivers want to find fares fast. But there are no switching costs for either side, so these network effects can be distributed over more than one platform.