I've always loved the phrase "prophetic minority." Coined by the journalist Jack Newfield, it neatly described the radicals of the '60s--the early edge who fought the first skirmishes on civil rights, protecting the environment, and other causes that eventually tumbled into the mainstream.

For me, though, there is another important and immediate application of this idea. I see a phalanx of consumers--millions, actually--who constitute another kind of prophetic minority. They are the vocal loudmouths who were bitching about the nutritional bankruptcy of McDonald's fast food years ago. They're the ones who first took on Nike for their child-labor issues, who championed open source software at the expense of Microsoft, and who think the rise of SUVs is an eco- and foreign policy disaster in fifth gear.

It seems pretty obvious that companies ignore the protestations of today's prophetic minorities at their own risk. They are the canaries in the cage of the consumer culture. Still, the denial continues. It's easy to dismiss these activist consumers as troublemakers--cranks and crackpots who have always been around, and will never rise to the level of a real business issue. In an age where preferences set over years are increasingly fragile and volatile, however, I believe that companies can no longer avoid the unpleasantness of unmediated voices.

The good news for entrepreneurs is that it is not hard to engage the prophetic minority. Companies must take the difficult step of eschewing the anodyne of traditional research--tracking studies and attitude and usage assessment--the entire armamentarium of probes. These measures are too polite, too distant from the roiling consumer psyche to be of much use anymore.

Instead, businesses should gather and study the authentic scribblings of the prophetic minority, which are everywhere--a kind of corporate graffiti. One obvious place to look for them is in the e-mail and phone messages received on a daily basis by your customer service reps. But the best place to find them is where you can find just about anything else these days: on the Internet.

In fact, what started as disorganized individual responses has now become neatly codified. Consider Yahoo. Do a search on the site for the "Consumer Advocacy and Information" directory, and then click on the "Consumer Opinion" category. Any company wanting to window into its market could do worse than spend a couple of hours here. The listings are many, and include PlanetFeedback, NetComplaints, and the Rip-Off Report, which assures visitors that the search engines will soon pick up their postings. Yahoo also conveniently supplies a list of companies facing boycotts.

Another valuable source for corporate graffiti is Google's user groups, which--it being Google--can be easily searched. I wonder how many CEOs type in their company's name--or their own, for that matter--and read the results, including the threaded conversations that are invaluable expressions of informed popular sentiment. And then there is Epinions.com, a well-known site which aggregates consumer feedback on everything from cars to camcorders.

Think of all these chaotic insights as a form of counterintelligence, the marketplace version of what the CIA calls "chatter." You don't need a mole to uncover it, just a mouse. And while some of these voices are acting on bizarre private grudges, there are thousands upon thousands of them that--when taken together--scale to a new kind of real-time market research. The vast majority of postings are thoughtful, motivated, passionate. Some are amazingly nuanced; I know some class-action attorneys who troll these message boards looking for actionable ideas--insights into bad billing practices, for example.

The value of corporate graffiti reaches beyond what it says about your business, to what it says about your competitors and the consumer psyche in general. The prophetic minority can and will burst into the majority faster than most managers imagine. Phenomena ranging from Howard Dean's insurgent campaign to smart mobs show the power of the Internet to transmit, organize, and influence. So don't shun the tracings of the future. The poet Robert Pinsky has written, "A country is the things it wants to see." And so, in truth, is a company.

Contributor Adam Hanft (ahanft@inc.com) is president of Hanft Byrne Raboy, a Manhattan-based advertising and marketing firm.