Comment by JadeNB

> in principle, the FOIA process gives the organization being requested time to think about what needs to be masked to protect privacy.

Although of course that's a lot more in principle than in practice! Like rolling your own crypto, I think experience shows that, against determined de-anonymizers, there is basically nothing you can do to preserve anonymity except to severely limit the information, and the only way definite feedback you get is if you don't succeed and someone discloses the de-anonymized information that they were able to reconstruct.