Bill Gurley has a great article on Uber’s valuation – actually a response to Aswath Damodaran’s piece – that raises some of the various markets Uber seeks to enter. He points out:
When I used to travel to Los Angeles and Seattle on business I would use a rental car. Today I only Uber. It is materially better. I do not have to wait in lines, and I avoid the needless bus rides on each end of the trip. I don’t have to map routes. I don’t have to find parking. I don’t have to pay for parking. The rental car market is $27B in the U.S. The global market would obviously be much larger. And you are also eating into the parking market here.
As a beneficiary of Uber’s recently reduced NYC rates, as well as an avid Uber rider while visiting other states, I totally see Uber’s ability to unseat the rental car market, as well as the broader car ownership field. Much like Netflix for movies, Spotify for music or the new Amazon book streaming service, Uber is about access, not ownership. And heck, I’ll take an on-demand ice cream cone any day.
Silicon Spatula 
They made the fares 10% cheaper so I can’t use the $30 referred from a friend discount on every ride.. well played, Uber