Earlier quoted context omitted.
Sorry, I think this is just totally disconnected from the reality of the average American who lives outside of a major urban center. 1. Mom, dad, and kid all need to go to work/school at roughly the same time. If they all have a 15-20 minute commute (well below average for many areas) and the destinations for all three aren't in the same immediate vicinity, we're right back to the family needing 2-3 cars. 2. Eh, no.…
1. Ok, maybe 2 cars if the locations are in completely disparate locations, but carpooling is possible. 2. User feedback could be a useful deterrent against messing up someone else's SDC, in the same way that both drivers and passengers can leave feedback with Uber today. 3. True, but one can adapt to this. Or maybe i'm just hopelessly optimistic... :)
My conclusion is that car sharing services are quite expensive. I can do no more than 3 or 4 short rentals a month before the cost start to resemble that of owning a used car. I do save money, but only because I drive a tiny fraction of what I drove when I did own a car.
Of course, car sharing is not as efficient as SDCs that can move around and maximize usage, but even SDCs would mostly end up parked at night and off-peak hours. Coupled with your point #4, I'm afraid it won't be long before driving the current average yearly mileage using those services become massively, prohibitively expensive.
I'm not sure how that would be a gain for anyone but the environment.