There are two events of interest to Muni this weekend: Critical Mass tonight at 6, and Supercross Saturday at one of the baseball parks. Both events are dedicated to the elimination of automobiles, but only one will actually accomplish its goal, while the other will just be a noisy, irritating echo chamber. Muni will be running extra trains to accommodate the Supercross crowd. The extra trains will stop running at 10pm, which is a......