Tweetups Can’t Touch Facebook Flashmobs:
"If you thought Tweetups were viral and picking up steam, you’ll never believe what one Facebook member was able to accomplish with a simple idea, a Facebook group, and proactive friends and friends of friends.
On January 15, T-Mobile filmed a commercial with people dancing at the Liverpool Street Station in London. After watching the ad on television, Facebook member, Crazzy Eve, created the group “Liverpool Street Station Silent Dance” to organize something similar for friends.
Here’s the choreographed dancing that inspired it all:"