The answer, as I see it, to this, is transparent decryption via federated ledgers. That way the data is not just "available".

Note- the big guys (facebook, google) could trick/force individuals into handing over keys, but if you make the keys per object this becomes less effective for the same big guys.

In a sense, there is no control without encryption.

Still cogitating the various hows, but transparency to the user is the key.