Decades ago, a marketing genius came up with the slogan “Everybody doesn’t like something, but nobody doesn’t like Sara Lee.” That’s not the case anymore. Sara Lee has been in the doghouse since last September when Hillshire Brands reformulated the brand’s signature pound cake because consumer panels suggested the product was “too dry.”

Big mistake. Big “New Coke” style mistake.

Consumers by the hundreds complained the company ruined their product, their holidays and their childhood memories. Consumer passions ran so deep that an innocuous article about the new product rollout is now one of the most commented postings in bakingbusiness.com’s history. Go ahead. Click on the item. You’ll find a good case summary of the sort most M.B.A. students encounter in their first year of graduate school.

And that lesson is, tinkering with tried-and-true products is a dangerous proposition. In fact, reworking baked foods to add moisture and softness has repeatedly spelled disaster. A few years ago, Brownberry reformulated its “dry” signature natural wheat bread only to go back to the original formula after a similar consumer revolt. Drake made the mistake years before when trying to make its snack cakes moister — and the tale of this, told by Theresa Cogswell, is also among our web site’s “most viewed” postings.

When it comes to America’s iconic products, the old adage holds true, “if it ain’t broke, don’t fix it.” And if you make a mistake, don’t wait six months as Sara Lee did before withdrawing its “new” pound cake. Cut your losses. Jeopardizing decades of brand loyalty is more expensive than you think. Apparently, nobody likes it when you mess with Sara Lee.