How could Digital's collapse be so precipitous? It's because, in many ways, financial performance data is misleading. As you move up to the top of the market, you're getting rid of the less profitable products at the low end and adding business with more attractive margins at the high end. The rate of unit volume growth might be tapering off as you pursue these smaller markets, but your margins actually look better. So Wall Street rewards your stock price until you hit the ceiling.

The answer is the disruptive innovator, an outsider, who creates a product or service for the non-existing consumer in a non-existing market for almost no profit.

We have found that companies need to speak a common language, because some of the suggested ways to harness disruptive innovation are seemingly counter-intuitive. If companies don't have that common language, it is hard for them to come to consensus on a counter-intuitive course of action.

In the study of management, unfortunately, many writers have been so anxious to articulate a theory in the form of, "If you do this, this will result," that they never go through this careful effort.

Disruption is, at its core, a really powerful idea, but everyone hijacks the idea to do whatever they want now.

But actually theory is very practical. Gravity is a theory, for example. It allows you to predict that if you step off a cliff you will fall; you don't have to collect data on that.

Whenever we have thanked these men and women for what they have done for us, without exception they have expressed gratitude for having the chance to help - because they grew as they served.