Welcome to the new future of involvement. Forming groups is easier than it?s ever been: unpaid volunteers can build an encyclopaedia together in their spare time, mistreated customers can join forces to get their revenge on airlines and high street banks, and one man with a laptop can raise an army to help recover a stolen phone.

The results of this new world of easy collaboration can be both good (young people defying an oppressive government with a guerrilla ice-cream eating protest) and bad (girls sharing advice for staying dangerously skinny) but it?s here and, as Clay Shirky shows, it?s affecting ? well, everybody. For the first time, we have the tools to make group action truly a reality. And they?re going to change our whole world.