There is a form of advertising that doesn't invade your privacy and doesn't need metrics. It is called "context sensitive" advertising. This is what happens when you go to a web site dedicated to pets and you see advertising related to pets. It's reasonable to assume you have an interest in pets; otherwise, you probably wouldn't be there. No metrics required. "Personalized advertising" is what happens when you go to…
Facebook isn’t a pets/cars/vexillology site, it’s an all-site; it and its kin are designed to contain almost all of humanity’s interests. It stands to reason that all manner of ads would fit in there, and in order to make these ads useful you need to filter or target them. If you see the history of targeted advertising, a case could be made that Facebook invented it as we know it today. No diss meant to Google and Googlers that might read this, I’m sure they played a big role as well.