The idea is that if enough people use ride sharing, the total number of cars needed will decrease, therefore, the needed space to put those cars will decrease. It doesnt necessarily require that everyone use it, but its about reducing the total number of cars necessary. If the density of these cars are sufficiently high, I can see a world where not owning a car is more convenient than owning one (if it isnt cost prohibitive).

This was the claim of ride-sharing about 10 years ago but studies showed the opposite, that it actually increased congestion.

Clean, effective, prompt, affordable, quickly constructed mass transit however, does seem to work.

I'm not anti-robo-taxi or pro-mass-transit. Instead, if the value is fewer cars and less carparks, mass transit with the aforementioned properties has been shown to work.

Sadly the United States has been unable to hit those notes with their projects (LA's metro, for example, is still constructing approximately the Prop A system approved by voters, in 1980, 44 years ago: https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Lo...) so in that specific case, it's murkier.

That world and system exists, its called public transportation and Europe

Even in europe a lot of people do own cars. If you have a friend network that really works you can manage without (we share two cars between 5 drivers), but realistically extremely cheap rideshare would be better for us in the long term (we lucked out on a deal with a car dealer who closed shop in a hurry, but now the cars are 12 years old and it start to show, even sharing the repair bills)

Extremely cheap ride share already exists, it's called public transit.

Small vehicles will never solve traffic, and will never be cheap, no matter the level of automation they implement. Labour cost is just one part of the equation.

Elon’s highly individualistic. I feel like his communal car-sharing society vision is at odds with that. How will that dialectic resolve?

Even if everyone does, you'll need enough cars to meet peak demand (which is a lot, especially with a 2 seater model).

Where do those cars go to charge outside peak demand?

Battery swap and back on the road. Obviously moving to this model would require changing conventional thinking. Cars don’t need to be parked, just like an IP address doesn’t need to “rest”. It’s just a pool of resources.

For starters, the average car is in use for less than an hour a day. With autonomous cars, it should be possible to raise this considerably - ie fewer cars standing around most of the day.

It seems to me that the average car is in use about the same hours of the day that all the other cars are in use, in front of me during my daily commute and clogging the roadways out of town on Friday afternoon

Owning a car and ride sharing are not even in the same category, unless you're of the opinion that the only purpose of a car is to get someone from A to B.