[al_gore]

This is true, but there's no reason that San Francisco itself couldn't have proper rapid transit instead of street cars. Even just removing cars from those streets and creating dedicated lanes (these exist in some places, of course) would be a huge help.

[koenigdavidmj]

The streetcars that remain mostly are still there for the Market Street Subway and the Sunset Tunnel. In other words, they are demonstrably better than an equivalent bus route in as-the-row-flies distance.