Flash Mob Gone Wrong

I found this on boingboing.net today. I watched it and again and again and again. And it is freaky! Tom Scott's Ignite London talk "Flash Mob Gone Wrong" is a fictionalized account of just how badly a flash mob could go. It's got a menacing ring of plausibility, largely because each of the steps leading up to the disastrous ending actually happened, just not all together. This whole chain of events can come together to trigger an undesired outcome. A frightening prospect, isn't it?