Note that a lot of the information being discussed is public information in the US though. Companies aggregate this information--often for a fee--but it's public by law. To take just one example that struck a lot of people as surprising when it became a topic during the last US election, in many states it's a matter of public record whether you vote or not (not who you vote for but whether you vote). And there are many, many other examples.

Historically, uncovering this information would have meant spending many hours going through files at county or town clerks--which put a very real limit on how widely it would be used. Now much of it is digitized (and aggregated). So at least part of today's issue isn't so much that private information is being made public but that ostensibly public information is now such much easier to access and cross-reference.