An innovation remains a fad until it becomes useful. Companies tried for decades to create touchsensitive personal communication and workflow devices that you can carry in your pocket. BlackBerry cracked the problem, but it would be the iPhone's app store that changed PDA smartphones from niche to mainstream.

A more striking example is Febreze, the US brand that removes bad odours. When marketed as such, it ended up failing miserably. But when it was marketed as a way to make your clean home smell fresher, it flew off shelves – and yet it is very good at removing odours. That's a lesson that the tipping point of an innovation can be hard to predict.