Uber has serious revenue. They do more trips in San Francisco than taxis do. This isn't a pie-in-the-sky "there will be money there, I'm sure of it" thing. They bring in billions, and they're starting to win entire markets.
The on-demand-transportation market is enormous. I can literally see a future in which the majority of the taxi industry is now called "Uber." That's a big freaking deal.
What Uber can do doesn't even stop at "transportation." How many "Uber for X" startups have you seen? Uber could be all of them, and do all of that. They've nailed the difficult math behind the logistics issues - basically a scaled version of the traveling salesman problem. They do real math, and solve real problems.
I imagine a world where you can get anything on demand in minutes, and in that scenario Uber is the taxi, UPS, FedEx, etc. at the same time.
In a few years when self-driving cars become the norm (crossing my fingers), Uber will be even more valuable. I may be dreaming, but empty cars you can grab any time and take anywhere or request anything... it really is a beautiful thing.