See InnovatorsDilemma.
ClaytonChristensen proposed that there are two major types of technologies, the usual SustainingTechology?, and the less usual DisruptiveTechnology. A sustaining technology is basically one that makes doing-what-we're-already-doing cheaper, or better in some way that the existing market desires. A disruptive technology is one that is proportionally more expensive, doesn't work much better, and basically is not desired by the existing market. However, the disruptive technology also has other qualities that make it desirable in some way to a small minority market. Disruptive technologies become disruptive when they have been improved to the point where they now compete adequately, not with the existing technologies, but with what the market desires which is often considerably less than what the existing technology is capable of providing. [Please feel free to edit some clarity into this.]
Christensen's big example is hard drive technology, but he also uses steel, excavators, and some others. His research is thorough and compelling.
Basically, disruptive technologies create the InnovatorsDilemma. You can't provide the disruptive technology because the market doesn't want it and won't pay premium prices for it. When the market suddenly wants the disruptive technology, it's too late for you to adopt it because the firms that made it popular will have a stranglehold on the disruptive tech's market (the pioneer advantage).
I see XP as a potential disruptive technology, which is one of the reasons why I think the best way of AdoptingXp is to start your own company.
Skype is a classic DisruptiveTechnology.
Can someone please explain why they see XP as a disruptive technology? One of the oft-cited characteristics is that it brings to market a worse product. How is XP crappier than traditional development methods? Disruptive innovation disrupts the business model of the incumbents. How does XP disrupt the business model of the incumbent? How are market incumbents doomed to fail at integrating XP into their company without forming a subsidiary or buying the disuptor?
XP is crappier because it doesn't permit the illusion of management control. This is also one of the costs of adopting XP by management, and XP's main customers are management, so XP is rightly perceived as more expensive than traditional top-heavy methodologies. XP disrupts the business model of top-heavy methodologists. Market incumbents such as die-hard advocates, or management consultants, of WaterFall are doomed to fail at integrating XP.
The analogy breaks down at the product stage. If XP is a technology whose product is software then its product is distinctly superior. On the other hand, maybe its product is programmer servitude .... But actually this is a red herring because the whole notion of product isn't what it's about. InnovatorsDilemma cites only "needs".
Management is currently stuck in a local maximum of control over deeply technical decisions (such as language choice) which they don't know anything about. The sub-market where it is critical to actually develop working software will adopt XP first, mortgaging management control over decision-making. Eventually, tools will be made to complement XP so that management gets more effective control over development. Unless of course management is completely wiped off the map.