First, I think that once a strong monopoly exists monopolistic dynamics persist throughout the integrated layers. This is a premise of anti monopoly legislation

First, I think that once a strong monopoly exists monopolistic dynamics persist throughout the integrated layers. This is a premise of anti monopoly legislation. Search, mobile, adwords, "advertiser tools" like google analytics, play store, youtube. Google have huge market share in each layer. These reenforce each other, amplifying the monopoly dynamics. Second, I think adwords could qualify as a monopoly on its own. Online ad markets have grown a lot recently, but circa 2008 (I think) adwords market share peaked pretty high even if you define "market" as "all online ads". The market can be defined more narrowly too. Third, EU courts have already found against Google for monopsonistic behaviour in their adwords market. Competing search engines monetizing via adwords faced some dirty tricks, but adwords was the only buyer.