2. Source? Outside of a few edge cases (china) I don't think this is a real concern. The same can happen with financial (or any) data, but I don't see people saying the data is the problem. Rather its the processes around that data that need fixing.
Advertising revenue is ad CPM (how valuable the ad is and how well it's targeted) multiplied by ad impressions (which is why people measure page views, time on site, minutes watched, etc.) Both matter in the model.
2. Beyond China and other authoritarian governments, the Cambridge Analytica affair is perhaps the defining example of this. It showcased nonconsensual data harvesting with malicious use of the data against those users to impact politics both domestically and internationally: https://www.nytimes.com/2018/04/04/us/politics/cambridge-ana...
Here another example from just a week ago: https://www.nytimes.com/2018/06/19/climate/koch-brothers-pub...
> "Central to the work of Americans for Prosperity is i360, the Kochs’ data operation, which profiles Americans based on their voter registration information, consumer data and social media activities."
In other words, the topic is the advertising where you give your attention to one party and that party participates (gets paid) to show you something else different from what you went there to see.
So, concretely: this is about paid ads on Facebook. This is NOT about products listed on Amazon that show up with compelling descriptions when you search for that type of product and clink on a link that wasn't higher in the list because someone paid for that.
When you go to Amazon and search, you are specifically choosing to put your attention toward products of a certain sort and asking for information. Amazon is delivering that information. There's marketing in how the products present themselves, but it's still something you are actively looking for, given to you second-party by the company from whom you are considering buying the thing.
When you go to Facebook to see how your friends are doing and your attention there gets sold to advertisers to show you unrelated products that may happen to fit your interests, that is the topic of discussion here.