Interesting point made by the author.

Its something I've wondered about. What would stop Google from degenerating? Its an interesting question because the reason we use Google (good search) is not how they make money (ads). They are related, but not the same. If you have a product that people buy, you have to keep making it better.

So what stops google from splashing their entire page with ads (to earn more), or not being the best in search (as long the ad revenue is flowing)? I think the author gives a good reason why google wouldn't do that -> because users will easily change their default search engine