I believe that visual ads is only the half (if not less) of Google’s revenue in general. The data which corporation owns is much more valuable than simple advertisement.
Think about Google Analytics and how much user activity reports they get from there. I am sure that the price of this data is big. All the ads are using analytics to deliver the right content to the right people, and almost every growing business will be happy to obtain this data.
Despite of analytics is not as distracting for users as showing ads, ad-blockers block its collection too. But analytics blocking can be easily avoided in many ways, which I cannot say about visual advertisements.
Thank the author for the good story on Google advertising!