We sold our car last year when we moved into the city. Even after accounting for the parking portion of our condo fee, we make strong returns on the obscene rate we charge annual renters. And no insurance, taxes, and maintenance pays for the weekly rentals I use through a car sharing service. I bike everywhere else, including to my tutoring gigs.
However, I don't think we'll be sans car for much longer. I'm tiring of old cars with questionable maintenance and strange odors, scheduling pickups and returns, and no longer having the option of RelayRides' hourly option.
Returning to a car is on the back burner now (and we could still park it outside of our garage spot so we'd not lose the rental option), but we make considerable income and are more Boglehead than Mustachian: I'd rather have something that's on demand, a known quantity. Maybe we'll rent it to a select few. Maybe not. But not everyone is given to permanently ditching the car - even those who have their spending, investments, and income in check.