New York Flash Mobs Met Their Maker:

The mother of all flash mobs officially came to an end on Wednesday night, in an inexplicable grand finale that amazed and confused both participants and mob organizers.

New York City's Mob Project was launched in May by a man known only as 'Bill' as an experiment in participatory street performance. People received an e-mail invitation to a mob event, where they interacted with others according to a loose script, and then dissipated just as suddenly as they appeared

(from Wired).