It would be the downfall of the Google empire (and probably half of the Internet) if the majority of companies realized that most of their online/mobile ad budget is absolutely wasted. I don't know of any other industry where people put so much money into it only to have so little tangible evidence at the end of the day of what they really paid for ("look, X real people clicked on your ad.... at least that's what we tell you and whatever that means for you.").