>... The Mafia? Any other criminal or terrorist organization or individual? The police operating under an incorrect warrant? A creepy ex?
The mafia is easy. Pay them and they DGAF what you do. Creepy ex is more or less a non-issue because any threat of violence one person can bring can be matched by another one person.
It's the police, terrorists and other well resourced but potentially capricious organizations (like the CDC, or any other federal bureaucracy, obviously the trigger happy ones are higher on the list), the kind of organizations who can send a dozen thugs to kick in your door and who have diffused responsibility across so many people you can't "get even" that you don't want coming after you.
>the CDC is at worst going to do what it thinks is best for you,
Every horror in history was committed with the best of intentions.
Edit: and to be clear, I'm not too worried about the CDC themselves, I'm worried about the legions of useful idiots that will happily take whatever they say and run with it. If the CDC makes BS or politically charged recommendations there is a myriad of other institutions (government and otherwise) that will see that as their ticket to do whatever bad thing they were already fishing for a reason to do. I don't want anyone having my data. But given the choice I'd rather have people who want to sell me penis pills and time shares have my data than people who want to tell me how to live.