Police Shut Down a 3k-Person Game of Hide-and-Seek at IKEA
The first (public) web app was a tool for managing large games of Assassin, which we used for about a week and a half to run a class-wide game until someone complained to his parents and the school shut us down. We probably could have finished it out, but once people get scared and start dropping out of an in-progress game, it's hard to keep going.