It was started by Improv Everywhere in New York, but this gala 9th pantsless year was celebrated (if that's the word) in 43 cities in 16 countries. Among those cities was Atlanta, although you wouldn't know it by the media's reaction. I'm guessing the folks who braved the weather on Sunday morning probably had the MARTA car to themselves.
I considered it, but allowed myself to be frightened off by the temperatures. Maybe next year.