My concern with this is the problem of ensuring the safety of the person driving the cab and the real identity of the rider. Lots of drivers will be reluctant because they can be stiffed on the bill. Lots of passengers will be reluctant to use it due to the inherent risk of riding with what is essentially a stranger.
BlaBlaCar [0] operates/ed only with community reviews (for drivers and passengers) and is doing just fine in EU... It is in fact so successful, that govs and press always talk about "services like blablacar and uber" (they're classified as basically the same kind of service) [0] https://www.blablacar.com/
For example the price you're allowed to ask is calculated to ensure it's only a cost sharing without any income for the driver.