> The recipients of those 9,000 ads are being trained to ignore the recommendations ... Likewise, a few clueless recommendations can “spoil” good ones shown at

> The recipients of those 9,000 ads are being trained to ignore the recommendations ... Likewise, a few clueless recommendations can “spoil” good ones shown at the same time. How can you be sure that "random" untargeted ads don't have just as bad of an effect? Ultimately Amazon can see the numbers and we can't, and they made their decision based on that. It's pointless to argue over theories without data.