"In battle, the commander is the first one to go over the top," Joe McKinney, shirt unbuttoned, wearing a shower cap and one of those aeroplane neck pillows, exclaims over music swelling from every direction. He's having a great time, romping around San Francisco as part of a "distributed dance party" -- a roving DJ set controlled by an FM transmitter, beamed to dozens of boomboxes, and led by men who look like Road Warrior extras drenched in neon paint. One of them advises through a megaphone not to step on or trip over a homeless man in the path of revelry.