Uber and Lyft operate in a space where there's a huge barrier to entry capital-wise.

This is not the case for 100% Internet based businesses like Facebook.

So they're really completely different models and therefore the competitive landscape can't resemble each other. It's more fair to compare the Uber-Lyft dynamic to rental car businesses like Enterprise-Hertz.

There doesn't have to be a single global monopolist. There probably won't be.

People do move, and the convenience of one app to hail taxis everywhere is appealing. But then again, people don't move that often that installing the local taxi app is too much of an assle.