Well, there's the entire field of databroking (likely completely illegal under GDPR, not to mention unethical from the start) and real time bidding related to t

Well, there's the entire field of databroking (likely completely illegal under GDPR, not to mention unethical from the start) and real time bidding related to this. Given the sorry state of privacy-compliance in general (whether that's ignorance of the law or consciously taking a risk) I seriously doubt that the field of adtech is much better.