Re: don't worry, our ads aren't as effective as we told you
I have known since I was about 10 that Coca-Cola tastes better than Pepsi-Cola. A few years later I learned a critical exception: Pizza must be taken with Pepsi rather than Coke, but the basic rule held otherwise. And a few years later came the realization that beer in its many forms is the only viable alternative to either.
All of this wisdom came largely from experience and the guidance of contemporaries. I do not recall ads that told me Coke beat Pepsi, but certainly there were some, and a comparable number of Pepsi-Cola ads that said the opposite. And the beer ads were probably more numerous than either, and as inconsequential. I suspect the same is true of Google and Facebook ads (as well as The Register's push, which I largely avoid with either AdBlock or uBlock.