Wouldn't matter. No one is interested in enforcing it, and there is too much value in the datapoint to credit rating agencies to tear the entire edifice down. Hell, back in 2011, I was part of a group migrating away from SSN usage at the Federal level. The biggest delay? Waiting for another semantically compatible I'd to manifest. TIN (taxpayer identification number) could be synthetically combined with a couple other ID's in the dataset such that they could finally retire the SSN's we weren't supposed to be using in the first place.
