The ACA simply requires everyone to have insurance and sets some guidelines about what that insurance must cover.
Part of the ACA requires doctors to turn over patient records to the FED's central database, through no agreement (or knowledge) by any individual.
I see this as being quite different in principle, from allowing or withdrawing agreement regarding those records with a private company having limited distribution of that data.
I've been able to live my life with relative anonymity. I wasn't fingerprinted as a child, never arrested. Heck, I wasn't even fingerprinted in the US Navy. I don't believe there is any legal reason for the FEDs to have my fingerprints, DNA, or my medical records.
Still, I'm sure I'm on some suspected terrorist watch list because I WAS in the military, and there is or was a record of me purchasing a gun (which is against federal regulations to retain). But, they don't really have a bonafide easy way to track all my movements or whereabouts...yet. Certainly the mandatory report of medical records allows one step closer capability to know where everyone is at any time (and what drugs they are likely to require to survive). I think there are very few people that can avoid a doctor's visit in their lifetime. Whether individual tracking was the original intended purpose or not. The effect is there and the capability can used in future actions without indemnifying any government individual or agency. Further, databases can be corrupted, altered, or hacked, which can put me at some unwarranted risk. All without my knowledge or agreement.
I'm well aware I do not have total control over my life. But, I am loathe to relinquish what control I do have, on a bureaucrats whim and with no possible benefit to me.