Photographer Spencer Tunick persuades people to strip naked in public places. These odd gatherings have attracted up to 7,000 participants, who for one day in their year, or possibly their lives, get to do something out of the ordinary.
The photos are impressive but, from an exhibitionist's point of view, they must be disappointing. The mass of bodies packed so closely together makes it impossible to identify anyone.
The anonymity is one of the great attractions of joining in a Tunick happening. By taking part, you can do something outrageous in public, but still enjoy the comfort of being part of a crowd. It's the same with chanting at a demonstration, swearing at a football match or pirouetting around a McDonald's paper towel in a flash mob.
Most of these events have a purpose. Tunick's human installations are part of his art, demonstrators hope to change society, and football fans try to intimidate their opponents. But flash mobs are pointless.
As we have all read a thousand times, the flash mob phenomenon first appeared in New York in June. They began as an act of spontaneous fun; an old prank using modern technology.
There's nothing new about organising events by e-mail or text message. The name came from two science fiction authors who wrote about the use of technology to organise and assemble rioters. Larry Niven described Flash Crowds in 1973, while Neal Stephenson coined the term Smart Mobs in 1995. In recent years, many of the protesters at anti-globalisation events have been described as smart mobs, as they plan events by e-mail, publicise them online and co-ordinate on the ground by mobile phone.
At first, this worldwide wave of pointless pranks sounded like a marvellous idea. Flash mobs were silly, but that was the point: they were pointless but fun. Arriving in the traditional 'silly season', when newspapers have little better to write about, flash mobs were whipped up into a global trend, and began forming in every large city in the world.