Hmm. Interesting thought but maybe not everyone without a car needs a bus? My favorite way to get around SF is an EUC. On the side walk, I'm a pedestrian, moving at 2 miles per hour. On the road I'm a car, moving at 30-40 miles per hour. In the coffee shop, I'm a guy with luggage. CALTRAIN is great for moving me and the EUC between San Francisco and Palo Alto. Truck takes me and the EUC to the coast for a swim.
(EUC = electric unicycle)