In July 2004, US cinema advertisements for Halo 2, the science fiction computer game, briefly carried the address for a website - ilovebees.com - which appeared to belong to a beekeeper who had mysteriously disappeared. Her honey-based recipes had been replaced by an apparently random list of numbers. Over four months 600,000 people joined in solving the mystery of what the numbers meant. What unfolded was a striking display of 'We Think': structured, mass collaborative creativity and intelligence.

If ingenious games designers can inspire thousands of people to collaborate to solve a puzzle, could we do something similar to tackle global warming, keep communities safe, provide support for the elderly, help disaster victims, lend and borrow money, conduct political and policy debates, teach and learn, design and make physical products?