What is disruptive innovation?

This is a question that I struggled with for a long time until I read Robert Burgelman's book, Strategy is Destiny. He offers a great explanation on Page 400. When reading the following, just substitute disruptive innovation for disruptive technology, as this is essentially what Burgelman is describing:

"Disruptive technologies focus on a different subset of performance dimensions in a product's multidimensional performance space. These technologies are typically rejected by a company's existing customers and therefore are not further supported within the company's resource allocation process. Often the internal entrepreneurs associated with such initiatives leave the company to start a new one. After finding new customers interested in the different performance characteristics of the technology, performance on the other dimensions also improves over time. As a result, the customers that were earlier not interested are likely to eventually find the new technology good enough and may switch. This leaves the incumbent companies still working with the old technology in a difficult strategic situation."

Another really important point is that a disruptive innovation is not the same as a radical innovation. A radical innovation is a major improvement along an existing performance trajectory. A disruptive innovation, by contrast, emphasizes a different performance dimension -- one that is not particulary important to incumbent firms' most profitable customers. This is often customization, convenience, or accessibility.

The superhero above is probably pursuing a disruptive innovation strategy: not strong enough to block breaks in the Hoover Dam; stop speeding trains; lift buses back on to bridges; or get in the national newspapers, as shown in the Superman movie; but he is good enough to rescue a couple of cats, or help an old lady across the street.