Ryan Moulton, a software engineer who has worked at Google for almost 15 years now, said in a HackerNews thread that the Google Search team and he personally have purposefully launched "ranking changes [in Google Search] that negatively impacted revenue substantially." He said this to drive a point that "there's an aggressive firewall between the ads and search organizations."
Ryan Moulton who goes under the alias moultano in the forum, said this in response to allegations in the thread that "it's not clear if it's still in Google's self interest to give users the best results anymore," and that all Google does it make changes to search that substantially increase the companies revenues.
Someone said in the thread "With Google featuring progressively more ads and Google content at the top of the results page, it's not clear if it's still in Google's self interest to give users the best results anymore." Ryan replied "This is why there's an aggressive firewall between the ads and search organizations. The ranking team isn't even aware of revenue numbers by ACL."
So then someone brought up "Apropos of anything else, Google is famous for a "monorepo". Any team can see the underlying architecture of things, regardless of any supposed "aggressive firewall" alluded to above." FYI, monorepo is the code repository. In which Ryan said "A monorepo does not let you deduce the revenue consequences of experiments, but regardless, even if you could figure it out, it isn't part of the incentive structure."
Then someone alleged that "if a search change demonstrably has a negative effect on company earnings (even if users like it) it will almost certainly be reversed." Ryan responded to that as well saying this is untrue and he has first hand experience showing the opposite. He said "This is completely false. I've personally been involved in launching ranking changes that negatively impacted revenue substantially. I didn't find out until months later through the grapevine, and only in vague terms like "ads had to scramble." Versions of them remain in production today. Revenue projections were never considered as part of the launch decision, nor have they they been consulted as part of evaluating subsequent versions."
Can you imagine finding out the Google Ads team "had to scramble" after you make a change that negatively impacts them?
Since I've known Google, this has been the line they have used. Google Search team in no way is influenced by the Google Ads team. Many do not believe it but Google has been consistent about this internally and even externally despite what "leaks" you may have read.
Forum discussion at Hacker News.