Leo Laporte talks about how well ads do on his network occasionally on his This Week in Tech show. I don't remember the exact numbers, but his revenues are millions of dollars annually.
For example, 90%+ of Youtube creators couldn't negotiate an ad deal like Leo Laporte because they are too small. Generalized ad services like Adsense/Youtube create income for the 90%, and personalization boosts that income allowing more people to produce more content.