[piokoch]

Information about can be used against you in many different ways: you can get higher prices in online stores (if, for instance, online store gets data that you are a rich person).

You can get higher insurance price if you insurer knows "something" about you or you can be denied insurance at all if they suspect that you are, say, an addict (and this does not have to be true, some "clever" AI will just qualify you as an 34% addict and good luck if such nonsense data, derived by some SF "move fast, break things" startup, will be interpreted in a sensible way by the insurer).

From the information Google/FB has they can derive that someone has a mistress and those who will learn that might try to blackmail such person. Or someone is looking for a new job and informed person can sell this konwledge to one's current employer.

[Karunamon]

This is non-responsive to GP's point, though. This is all hypothetical. Where's the actual, concrete, demonstrated harm?

"Someone in the future might do something untoward" is not concrete.

[rendall]

GP's point was that they could only think of bad things happening if these companies leaked personally identifiable data. If I have not successfully addressed that specific point, demonstrating that there are worse things, then I do not know how to.