Hailing a self driving car?
"With the ability to just hail one (probably for a darned sight less than the total cost of owning a car) will leave most with little reason to buy their own"
Newflash - there are already these things called "taxis" (maybe you've heard of them?) that you can hail that have been around since before the internal combustion engine was invented. Oddly it hasn't stopped people buying their own cars. Also the chances of anyone who's forked out a small fortune for a car just to let it become an unsupervised taxi where drunks can throw up with impunity or try and still the contents or fittings I suspect is pretty damn slim.