You're with Walmart. It's 2009, and you want to do something new, something transformative, to out-innovate rival Target. You have a sense that Target is cleaner, better designed, less cluttered. Walmart aisles are crammed, packed, an infinite jumble of product.

So you're thinking of launching an uncluttering project. Strategic. Huge. Millions of dollars. But before you make any changes, you want to float the idea by customers.

So you conduct a survey, asking customers: would you like Walmart aisles to be less cluttered? And they say, "Yes, now that you ask, yes, that would be nice." And you check the box by "customer input" and report back, hey everyone, good news, yes, customers like the idea.

Walmart spends hundreds of millions of dollars uncluttering their stores, removing 15% of inventory, shortening shelves, clearing aisles. Yes, it's expensive and time-consuming, but this is what customers said they wanted, so you barrel through it.

You'll never guess what happens now. (Actually, you've probably already guessed, but it sounded better to say you'll never guess.)

Sales went down. Way down. I mean waaaaaay down. I'm talking, from the beginning of that project until today, Walmart has lost over a billion dollars in sales. (Yes, billion with a "b".) It's actually closer to two billion dollars of sales they missed out on, and maybe more.

Needless to say, the executives in charge of the project have been fired, and Walmart is spending yet more money to return to its original, time-tested strategy of offering a huge (albeit cluttered) inventory at low prices.

But wait. Before the lost sales, the fired executives, the mad scramble, before all that: what was the billion-dollar mistake that caused this mess in the first place? You'll never guess.

The mistake was a lack of customer focus. I know, I know: "They ran a survey! Customers loved the idea!" But that's exactly the problem. Walmart didn't pursue the question of what customers wanted. Instead, Walmart came up with the answer first, then asked customers to agree to it. That's exactly the wrong thing to do, because it ignores customers while attempting to fool stakeholders into thinking that the strategy is customer-centered.

Put another way, Walmart based this incredibly expensive misadventure on what customers said, rather than what they did. And the customer experience is all about what customers do. In real life. No hypotheticals. Walmart acted without considering the customer experience, and that was a big mistake. (Maybe the biggest mistake a business can make, if you ask me.)

The lesson: ignoring the customer experience is an expensive mistake. Be sure to listen to customers the right way, so that you get a strategy that actually works. (And let me know if Creative Good can help. Maybe we can save you a billion dollars. That's always fun.)

P.S. For more on this story, read Phil Terry's Daily Artifacts post, which includes lots of numbers and links to press coverage. Thanks to Phil for pointing out the story.