Privacy

Researchers long ago showed how combining two or more sets of data allowed them to effortlessly de anonymize data with computers programs. That has been known for at least 2 decades, back when it was maddening and worrisome but not yet an existential threat to representative democracy and our wellbeing, before malign forces weaponized the unprecedented mass of data now collected, in ways we don't even know about yet.

Plenty of people with anonymous accounts on social media have been identified also by groups to punish them for comments, typically ones critical of Israel, supposedly identified as such, but it could be just as likely the US government leaked the information to them, or the social media company. But combining all the information you have let slip narrows it down considerably if a computer is used to sort all the information.