Re: How far will Google to protect...
"Isn't Google itself the biggest ad platform?"
Different kind of ads - The paid search ads that appear at the top of your search pages aren't affected by ad blockers and are plain text. Google is the biggest cheese in that context. For simplicity, I'm including Google Shopping in this category.
Youtube video ads are affected by adblockers but are HTML5 videos as opposed to flash or Java and as such, I'm not aware of any exploits that will get you screwed over. Because of youtube, Google is probably the biggest provider of video ads.
The ads this change affects are known as display ads. Google is a major player in this space but have nowhere near the dominance in the search and video channels.