The term 'flash-mob' usually conjures up images of people stripping a store of its contents en masse, or a lightning strike demonstration by a group of concerned individuals.
I like flash-mobs, I may not agree with something they are demonstrating against or for, I certainly don't agree with a pack of criminals picking some poor sod's shop clean, but I do like the dynamic, especially in terms of demonstration, where a group of people can turn up and leave the authorities completely exposed and unprepared for the crowd. There's something energising about it, even if it can result in destruction of property and vandalism. I suppose my delight comes from the fact that some people still realise that they can get together and organise themselves without the all pervasive hand of the State coming in to co-ordinate.
There are many motivations for flash-mobbing, and the below is one of the most beautiful I've seen, or more correctly perhaps, heard. The motivation here is commercial, it is clearly a low-cost, viral ad. But it is a thing of rare beauty.
Sit back, watch, listen, enjoy and think how thrilling it must have been to have had that going on about you with no warning at all.