This newest flashmob took place in London several days ago, and all started when a Facebook member saw a TV commercial for T-Mobile.
Inspired by the dance routines in that commercial, he invited a couple of friends to the station so they could have a little fun.
And of course, with the way social networks operate, a couple of friends invited their friends, who invited some of their friends, and this eventually turned into 17,000 people making their way towards Liverpool street station.
Check out the video for yourself. The event was so successful that more of them are being planned, but nothing beats the spontaneous kind of gathering put together by a single Facebook message.