The problem is that they can't do that to completion- they often can't know the data that their advertisers are collecting and they certainly can't share the da

The problem is that they can't do that to completion- they often can't know the data that their advertisers are collecting and they certainly can't share the data that they're collecting from 3rd parties using 'profiles'. An important fact from this article is your privacy is often the minimum of the privacy settings you have set. So it might be true that you've never authorized Vox to monitor your demographic data, but they know enough to get that information from other companies. Legally they can't share that information.