Proctor & Gamble was not certain it was getting a good return on its $100 million digital ad spend, so one day they stopped.
They found no change in their sales. Of course, no one listened. It is still buy, buy, buy! in the digital ad world.
I do worry that the P&G article was fake news (from P&G) as I cannot imagine any company, let alone a huge conglomerate, spending $100 million per year without a mechanism to learn the ROI quickly.