I'm not sure its the PMS or just seeing something that makes people so pleased. T-Mobile created a commercial at Liverpool station in England arranging a dance flash mob to begin dancing at 11 AM. The dancers were asked to try and pull in spectators as much as possible. Here is what happened...
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Here's a the "making of" video:
http://www.youtube.com/watch?v=uVFNM8f9WnIThe reactions:
http://www.youtube.com/watch?v=9Jv6rHJiNhQ