Dominance comes at a cost — Google and Facebook are facing growing antitrust scrutiny and pressure from regulators over their dominance of the online advertising sector, and Warc cites this as a potential reason to expect slowing growth from both companies going forward. Google in particular has seen its advertising business slow as it reaches massive scale — and, hence, saturation in developed markets — and consumers push back against the type of tracking that makes its advertisements so valuable.
Nonetheless, Google recently broke out revenue numbers for YouTube and we learned that the business is growing rapidly, confirming what we've long suspected: TV is in trouble. Unless regulators decide to step in and reign in the duopoly it's unlikely that trend will change course.