It’s time to dump the myth of the Great Brand.

Take the case of Ford. In 2001, Interbrand valued the Ford brand at some $30 billion. By this year, it was down to $8 billion. Did Ford really manage to undermine 98 years of history and marketing in seven years? Or is it a lot more likely that the brand was never worth anything like $30 billion in the first place? Even the new, smaller number is an absurdity—it's bigger than the total value of the company's stock. If Ford closed down tomorrow, does anyone imagine that some less-known company would pay $8 billion for its famous name?

The Interbrand list is full of this kind of preposterousness. American Express' brand is worth just a shade less than the company as a whole, at $22 billion. It's unquestionably a well-known name. But how much would it be worth if people no longer wanted its products and services? Would it be more or less, say, than the $7 billion value that Interbrand places on the brand of disgraced insurance company AIG? Microsoft's brand is at No. 3 on the Interbrand list with a "value" of $59 billion. Does anyone think Microsoft would sell any fewer copies of Office if it changed its name tomorrow? There are many reasons why Microsoft is a very prosperous company, but its customers' ineffable affinity with the brand isn't one of them. For $59 billion in cash—that's about two years and nine months of Microsoft's profits—Steve Ballmer would probably be willing to change the company's name to Lehman Bros.

None of this will come as news to most of the companies you think of as having really great brands. Underlying the best brands are usually sales pitches of great stuff. Macs don't crash. The iPhone 3G is fast. FedEx gets there every time. The Lexus parks itself. Canon is the professional's camera. Even Pepsi—the company that more or less created modern branding with the slogan "The Taste of a New Generation"—decided in the end that, actually, it was easier to sell soda with the Pepsi Challenge taste test. At the very top of the Interbrand list you will find Coca-Cola, the great outlier of the brand world. Far from the model of how brands work, Coke is the great exception. The vast majority of great brandmakers knows that you cannot sell products by telling people about your brand—you can sell your brand only by telling them about the product.

This is the basic principle that brand managers at Procter & Gamble have had drummed into them for decades, but it goes against the grain of the Intangible Economy of the last decade. The brand myth made marketing about something classier and groovier than actually selling stuff. It turned selling into a gentleman's art, and, by separating it from the drabness of actual products, made it seem like an engaging pursuit for the well-educated grad who didn't want to go to law school, something to add to the dinner-party chatter.

Like so many of the great intangible values treasured by the new economy—the hidden "savings" in real estate, the U.S. financial industry's infinite reservoir of know-how—the enormous value added by the wizards of the branding world turns out to be a figment of a feverish accountant's imagination. After this dismal Christmas season, the marketing gurus will probably tell us that billions of dollars of brand value have disappeared. There may even be a list that will add up exactly how much. But for the end of the era of the Great Brand Myth and the reign of the marketers who peddled it, there will be no big announcement or BusinessWeek cover story. Just the slow fading-away of another big idea whose cultural moment has passed.