> With regards to cars, I get the sense that the most realistic future is no longer mass-transit only, but includes self-driving electric car-sharing.
I see this as likely too, but I also can see the downsides to it, because people suck. Just think of how mass transit looks like in your city, and how people treat rental cars, rented housing, etc - and apply that to shared vehicles.
Though to be honest, we could make a better comparison today to things like Zipcar; I've never used one, so I don't know how often - if at all - one climbs into a car only to find it beaten to hell and back with vomit in the seats? Then again, such services aren't ubiquitous in all cities, so fewer people use them, and they might be more expensive so that those with a worse sense in using other's property are less likely to use the service?
I just know that with rental cars ("drive it like you rented it") and rental properties - it's hit or miss whether the renter(s) are going to be careful with the property and upkeep of it, or if they are going to utterly destroy it (usually, it's probably somewhere in-between, tending toward taking care of it). You'll always have those outliers I guess.
For now, though, I am keeping my vehicles, and paying the price. For one, I can't easily rent what I own (both vehicles are four-wheel drive and designed for off-roading), and one of those vehicles is a fairly rare machine (only about 5000 were sold in the United States). There are times, though, that I have been thankful I could rent a vehicle or take a cab or similar; sometimes you have no choice, or it's the better thing to do for the purpose at hand. In the future, with self-driving shared vehicles, this will be welcome for many purposes - but there will be downsides (likely, the first person to get the "destroyed vehicle" would decline it with a reason and it would be sent back to a depot for refurbishment).