To prop up the stock price, managers have to turn down the screws on everybody. That forces them to cancel all the projects that would lead to future growth in order to drop money to the bottom line. This is HP's dilemma today. Once a company's growth has stopped, the game as we have known it is over. It's a scary thing.

I've concluded that getting the categories right is an absolutely crucial step to building useful management theory, and unfortunately too few writers do this. You've got to engage in serious scholarship, and then figure out how to write it in a way that lots of people can understand.

The important thing is that over time, scientific progress transforms things that used to have to be dealt with in a problem-solving mode down to the pattern-recognition space; and from pattern recognition into the rules-based mode. This is the mechanism by which less-trained people are enabled to do more sophisticated things. This is always the way disruption happens. It enables a larger population of less-experienced people to do more sophisticated things.

In my first career I had founded my own company, with a group of MIT professors, before coming to Harvard to finish my doctorate, and so I had a deep respect for the brains, talent, and dedication of managers. That made it hard for me to believe the attributions in the business press that stupid management was to blame. So I looked elsewhere for an explanation.

Management has to provide the coordinating mechanism between what the supplier provides and what the user needs in not-good-enough situations where product architecture is consequently interdependent. Management always beats markets when there is not sufficient information.

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.

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