These developments have come under a lot of scrutiny, and much of the published reaction to this new role for public opinion has been positive. The “wisdom of crowds,” to borrow the title of the best-selling book by New Yorker columnist James Surowiecki, has become one of the hot ideas of the past couple of years. And there is a lot to recommend the idea, as anyone who has used the Google search engine (that is, everybody) can readily attest. Surowiecki’s book opens with a couple of breathtaking examples of the wisdom of crowds, and explores how it is possible for a group of non-experts to come up with a better answer to certain kinds of questions than any individual expert can devise. He is also careful to specify the sorts of questions that crowds do better with, and those they tend to fumble. Another fascinating exploration of this terrain can be found in Infotopia: How Many Minds Produce Knowledge, by Cass Sunstein, the distinguished legal scholar who is just moving to Harvard Law School from the University of Chicago. The idea has obtained a life of its own on the Web and in society at large, where boundless confidence in groupthink prevails. (This has been attacked as well, of course, in such books as Andrew Keen’s The Cult of the Amateur: How Today’s Internet Is Killing Our Culture, a passionate defense of professionalism.)

The best way i know to think about all this is as a consumer. I am a careful shopper, and I’ve always been the person my friends ask when they want to buy a car or stereo or TV. In the past decade, the amount of information available on such products has grown exponentially, as has the variety of sources. The careful consumer has a lot of work to do these days if he or she wants to be thorough. Let’s take car shopping as an example.

How do you buy a car? It’s a big decision in any family, and it’s natural to try to get some kind of help (particularly because car salesmen do not have a sterling reputation). One place consumers turn is the press, which runs articles about car safety; reviews of new models; technology pieces on new automotive gear (navigation devices, hybrid engines, safety systems); and business articles about the auto companies, the insurance industry, and so forth.

For years, car-enthusiast publications, consumer magazines, and newspapers have reported on such matters. But today, this expert sort of testimony has been supplemented, and even challenged, by new sources of data. As a careful consumer, I have honed my research methods as the information ecosystem has evolved.

In fact, I am now in the market for a new car. Fortunately, I have a lot of resources that were not available when I bought my first one, a $300 beater, a quarter-century ago. Before I do my own in-person reporting—a.k.a. the test drive—my research relies upon the testimony of experts in the automotive press, the combination of polling results and expert assessment from Consumer Reports, and similar mixes from Web sites like Edmunds.com, cars.com, and Kelley Blue Book. Invoice prices, not just of cars but also of options and option packages, are a snap to find. Available colors, incentives, and so forth are but a click or two away. At the cars.com site, meanwhile, I can find reviews of cars drawn from newspapers and other sources.

But the bigger change is that online the “experts” are being supplemented, and sometimes nudged aside, by the aggregated opinions of consumers (or interested parties masquerading as consumers). Such vox pop input has become a familiar feature on sites like Amazon, Netflix, and so forth. These entries serve as a reminder that the “wisdom” of crowds is aggregate—individual entries can be pretty terrible. But when forty or sixty or eighty consumers weigh in, the results can be very helpful.

Evan Cornog , former associate dean for academic affairs at Columbia's Graduate School of Journalism and the former publisher of CJR, is dean of the School of Communication at Hofstra University.