A journalist investigated the complex web of companies through which data about his movements was collected via his phone and redistributed, ultimately reaching the US deportation thugs.

He concludes that the GDPR are not, in practice, doing much to prevent this sort of spying. Also that anonymization of the location dossier does hardly any good.

He warns that this sort of data can be dangerous "in the wrong hands". It is crucial to realize that there are no "right" hands. We must design systems so that they can't be used to snoop on people.

If this makes targeted advertising impossible, great!