alt Hacker NewsI agree, but I think the concept of data provenance would have a role. It should not matter if data is laundered through 'aggregation' or 'anonymization': if it was originally generated about an individual, and used to target an individual, that data should be an expensive regulatory liability.
The answer is that (approximately) every ad you see is targeted based on (approximately) everything you've ever done on the Internet, every purchase you've made in-person or online, and every location you've been to physically.
I don't think attaching a disclaimer like this to every ad will be impactful at all.