What would it take for somebody to just build a free, open-source matchmaking service for drivers and riders? It doesn't seem like what Lyft or Uber offer is very technically demanding (perhaps doing it at scale is), and presumably you could attract a lot more drivers by offering them the chance to keep ~99% of the fare. The existence of Lyft demonstrates that Uber's first-mover advantage isn't insurmountable, so who…
Who would provide customer service, sales, marketing, user research and the other non-technical elements of the business? It's true of many companies that what they do is not very technically demanding (Amazon, Facebook, eBay, etc) but that very often means that you _can't_ replicate them by just replicating the technology - these successful companies are much more than just their software. And anyway, I bet there is…
Do you need any of those things? How much does Craigslist spend on marketing and sales?
Operate as a non-profit, compete only on price, and let drivers spread the word themselves. Imagine if at the end of the ride, your Uber driver told you, "Hey, next time call me with the CheapRides app and it'll cost you 20% less, and I'll make more."