In 2013, eBay did something almost no marketing team would volunteer for. They turned off their branded search ads and waited for the damage. The economists running the experiment expected a measurable hit. What they found instead became one of the most quietly ignored studies in the history of digital advertising: branded search had no meaningful incremental impact on purchases. The people who clicked those ads were already on their way to eBay. When the ads disappeared, the same people arrived through the free organic listing sitting one inch below where the ad used to be.

The industry read the study, nodded, and went back to bidding on its own name.

Twelve years later, branded search is still the campaign with the best ROAS in most ad accounts. It is the line item the CFO loves, the screenshot that opens the quarterly review, the proof that performance marketing works. And a growing pile of incrementality research says a large share of that performance is a heist. Not fraud in the legal sense. Something more comfortable and more expensive: a measurement system that hands your ads credit for customers …