I don't own a car and instead use a ZipCar-like along public transit and cycling. My conclusion is that car sharing services are quite expensive. I can do no m

I don't own a car and instead use a ZipCar-like along public transit and cycling. 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.