Do you remember flash mobbing? It was a silly summer craze that broke out a couple of years ago. Crowds of strangers in their 20s and 30s, mobilised by e-mails or text messages, would converge on a public place and engage in a seemingly spontaneous act of absurdity such as waving bananas in the air or speaking without the use of the letter "O".

It would be hard to imagine any thing more pointless. But perhaps that was just the point. Whatever else it may have been - a bit of a laugh, a minor thrill - there was more than a hint of anarchy about flash mobbing. Operating outside all bounds of economic rationality, it was in many ways anti-commerce. Those who joined the mob were momentarily refusing to act as market participants; instead, they were doing something that cost nothing, benefited no one and brought no company any profit, just for the hell of it.