Who owns a brand? Lawyers will tell you it’s a matter of copyright and trademarks. But that’s bull. Your customers own your brand—100%. Every little bit. When consumers think of BMW, they’re believing that if only they owned a BMW, they’d be the Ultimate Driver of the Ultimate Driving Machine. BMW’s job is to never defame its brand essence. Imagine a BMW ad that boasted, “Now available in a gas-saving hybrid!” Sure, they have the hybrid, but they don’t want you to associate any benefit except ultimate performance with that $70,000 vehicle choice. When you have a successful brand, you tamper with it at your peril. It’s not yours to adulterate.

Nike (helped by the Wieden + Kennedy ad agency) showed branding know-how when in 1988, it urged its customers to “Just do it.” And when they supplemented it with the “swoosh,” history was made. But once created, a great brand is not always easy to keep safe. When Nike’s spokesperson, Tiger Woods, slipped up in his personal life in 2010, the brand took a beating too. Finally the company decided that the two icons would stay together—for now.

Some branding stories are rockier. Wendy’s comes to mind. Dave Thomas was the founder and CEO of this fast-food chain and for many years its spokesperson, appearing in over 800 TV commercials. A survey taken in the 1990s purportedly revealed that 90% of Americans knew who he was. When he died in 2002, the experts wondered what will Wendy’s do? How will they replace Dave?

The next decade was painful. They introduced Dave’s daughter, the “real” Wendy. That didn’t work. They ran “our burgers taste better than theirs” ads. Boring. The nadir came in 2004 when an ad agency had the grotesque idea to have a young man pretend to be Wendy. Having a “Mr. Wendy” probably sounded brilliant in the pitch, but customers hated it. Wendy’s is their brand. Recently, the company seems to have come up with a winner in Morgan Smith Goodwin, a red-headed spokesperson who evokes the image of an authentic, real Wendy. She clicked. At least for now, customers are satisfied.

Some cynics insist that branding is hot air, a myth ad agencies invented to justify their existence. They’ll tell you “the best product will always win out in the end.” Here’s my experience. Not too many years ago, my agency was awarded the account for an osteoporosis prescription medicine. It had great data. My main competitor was Boniva, also an Rx drug with a similar MOA, but clearly second-best. When we got the assignment, I licked my chops and prepared to launch another blockbuster. Then Boniva’s agency ran a series of DTC commercials featuring Sally Field. Patients loved her. I never had a chance. Boniva killed us. I have to take off my hat to my rivals. Coming up with Sally Field wasn’t easy. Branding’s hard, but when it works, it’s a game-changer.

If you still think branding is easy, I have a challenge for you. Henkel (Schwartzkopf in the US) is a worldwide leader in women’s beauty products. According to the Wall Street Journal, Henkel is launching a line extension of its successful Gliss shampoo, which will be marketed to Muslim women who wear a scarf. The USP? The first shampoo specially formulated to treat “hajib-hair.” Brilliant! So here’s a puzzle for all you marketers. Given the market niche, if you’re Henkel, how would you brand your new shampoo?

Sander A. Flaum, MBA, is principal, Flaum Navigators, and Executive-in-residence and chairman, Fordham Leadership Forum, Fordham University Graduate School of Business Administration.