In two days, if you don't know what's coming, you might find yourself in a puzzling situation — here in San Francisco or pretty much anywhere in the world. Let's say you're taking your lunch break on Friday. You're in line at an ATM when you notice someone dancing nearby. She's really into it. She has no intention of stopping. “Oddball,” you think. Then someone cranks up a car stereo and joins her. Across the street in a courtyard is a group of people doing synchronized steps. Then you spot three more on a corner. Is there something going on you don't know about? You bet. It's Dance Anywhere, a coordinated effort to get people around the world to dance at the same time, wherever they are.