With a model more like Car2Go (pick up the car wherever you can find one, leave it wherever you want to) this isn't as much of an issue. In Austin there's pretty much always a car within a few blocks... almost "driveway-level" accessibility.
And if even 10% of drivers switch to using this model, then there's always going to be a car on your block. That's pretty competitive.
With driverless cars it's even less of an issue, because the car will literally drive from the end of the block (where it's waiting) to your door.
Assuming, that the San Diego prices can be applied to Francisco, it seems like taking such a car from downtown to the airport would be about the same as the BART subway.
I assume, that would be too expensive for a daily commute.
And if even 10% of drivers switch to using this model, then there's always going to be a car on your block. That's pretty competitive.
With driverless cars it's even less of an issue, because the car will literally drive from the end of the block (where it's waiting) to your door.