The bad news is that the odds are stacked against even the best-run companies. Strangely enough, the principles of good management can lead companies to fail.

The downfall of a seemingly unstoppable market leader almost always follows a predictable pattern. It starts with a company doing what it is supposed to do . . . improving its core offering to meet the needs of its best customers. In doing so, the company overshoots the needs of less demanding customers at the market's low end. It increasingly ignores seemingly fringe markets of "nonconsumers" who find existing solutions too expensive or too complicated.

Then a disruptive innovator comes and changes the game. The disruptor starts innocently, bringing a simpler, more convenient, cheaper solution to customers that the market leader views as irrelevant. Over time, the disruptor improves its offering and marches into progressively more demanding market tiers.

The former market leader either loses its dominant position or remains the titan of an increasingly irrelevant market.

Companies like Apple, Cisco, eBay, Wal-Mart, Toyota, Sony, Nucor Steel, Procter & Gamble, Southwest Airlines, ING, Salesforce. com and Intuit all assumed their current leadership roles by being disruptive innovators at one point in their histories, reshaping portions of their respective industries with new products and services.

Healthcare, media and software provide three pertinent examples of disruption in action today. And while history teaches us to bet against established market leaders, companies that see opportunity in disruptive threats can tilt the odds in their favour.

Media: Ten years ago it was Monster. com and eBay. Five years ago it was Yahoo! and Google. Two years ago it was the blogosphere. Today it is MySpace. com (purchased last year by Rupert Murdoch's News Corporation) and YouTube. com. In each case, innovators are democratising an industry that historically has relied on centralised production and distribution.

As newspaper readership sags, TV and radio audiences splinter and teenagers hang out online instead of at malls, what is an established media company to do? Our work with the American Press Institute gives us great hope that established media companies could be at the beginning of a new golden age. More information is being created and consumed than at any point in history. Forward-thinking companies can reach consumers that historically eschewed their core product.

There will be winners and losers, for sure. Media companies hoping to succeed must break from their historically centralised models or risk becoming increasingly irrelevant. They should look at how MySpace builds communities and enables collective conversation and how YouTube aggregates user-generated and usercontributed content.

Established companies are beginning to figure this out.

Cox Communications recently launched Kudzu. com, a website where users rate local service providers like plumbers. NBC struck a deal with YouTube to distribute promotional content. And the Dallas Morning News is creating a website with lists, databases, guides and community features aimed at local mothers.

Healthcare: Disruption almost always strikes industries characterised by high costs, inefficiency and widespread customer dissatisfaction. Does any industry fit the bill more than healthcare?

Consider MinuteClinic, one of the leading providers of diagnostic kiosks in pharmacies like CVS in the US. In fact, CVS purchased the company in July for close to $200m. MinuteClinic's nurse practitioners can diagnose about 20 common ailments, such as strep throat or pink eye, in less than 15 minutes. When the diagnosis is positive, the nurse practitioner writes a prescription on the spot.

MinuteClinic and other emerging providers offer low prices and unbeatable convenience.

Some medical device manufacturers are driving disruptive change by making it easier for lesser-trained medical providers to deliver great care. Ethicon EndoSurgery (a division of Johnson & Johnson) has a history of making invasive, difficult surgical procedures simpler and more affordable. Dutch conglomerate Philips sells a home defibrillator that allows individuals to treat sudden cardiac arrest.

Software: SAP, Oracle and Microsoft have a combined market cap of over $350bn. As these companies have evolved over the past decades, their solutions have got progressively better. They have also become more complicated and more expensive. Each now faces disruptive threats.

SAP and Oracle are under siege from simple, affordable solutions like MySQL, Salesforce. com and Intuit's QuickBase offering. Microsoft faces threats from companies like Google that are offering "good enough" versions of Microsoft's desktop software for free.

The opportunity for today's software leaders is to figure out how to create compelling offerings to serve businesses that historically seemed too small to matter to them or, as Microsoft is attempting to do, to move into web-hosted, collaborative environments. It will be a challenge for the historical market leaders to harness their impressive engineering talent to tackle these new problems.

Clearly, disruptive forces are at work in just about every industry. Market leaders who ignore or dismiss these forces do so at their own peril. As more companies understand the patterns of disruption, however, market leaders need not be powerless. Acting appropriately can allow them to use the power of disruptive innovation to write their own success stories.

Clayton M Christensen is the Robert and Jane Cizik professor of business administration at Harvard Business School. Scott D Anthony is the founder of innovation consulting firm Innosight. They co-authored, with Erik A Roth, the book Seeing What's Next: Using the Theories of Innovation to Predict Industry Change.