Good point. I think the state will have to take on the liability.
The future is not only self-driving cars, but roads composed of only light-weight self-driving cars. In such a system, where, in order to maximize efficiency, the safety offered by heavier vehicles has been compromised, it may make sense for a centralized agency to ultimately vouch for and maintain the vehicles on the road.
Furthermore, I see no reason why these vehicles can't be shared, like taxis. That eliminates the need to park, which eliminates parking lots. It eliminates public fueling stations, it eliminates the complexities of home charging (especially for urbanites). The vehicles are simply rented for a time, and returned to the herd. In dense urban areas, they can be sitting outside, waiting a hail. In suburban areas, maybe a text from your cell phone will bring one to your location in minutes. In very rural areas, perhaps people will be licensed to buy and keep their own vehicles.
Make no mistake, once the public is more aware of this technology people will demand it. Like cell phones and the Internet, I (and many automotive insiders) expect it to take over in a relatively short amount of time. Liability is perhaps the last major hurdle, and I see no other solution than this sort of transportation being taken over by the state, as has been other shared, ground transit.