The primary problem is going to come the first time a driverless car is involved in a serious accident.
Since there is no driver, just passengers, how can they be liable for damages or deaths that are caused when the driverless car is involved in or causes an accident?
Does the liability fall back to the manufacturer of the car? Or the programmer that wrote the code for the car?
What company could accept the liability for all those cars they sold to the public?
Or would that be the issue, they can make the cars for $35,000 but the added liability coverage would be to expensive for most to afford.
Of course the real problem being discussed here is driverless cars sharing the road with idiot drivers doing stupid things everyday. They will be involved in accidents and they will cause major damage at somepoint.
The only way to solve that is to switch entirely to driverless fleets of cars instantly, and that is not something that can be done. Costs would be to much.
This can also be a very disruptive technology. I expect the first real commercial use for this would be long haul trucking. Setup a fleet of these driverless trucks and run them from depots on or near the interstates. They can run as long as they have fuel which should improve the transportation costs since the trucks don't have to stand down every 8 or 10 hours to allow the drivers to sleep. And being on limited access highways the chances of them being involved in situations that are unforeseen are minimized. Once at a depot loads can be shifted to normal trucks for delivery in towns.