Random things that come to mind, with no attempt at completeness:
Check what authorities of the place you live are willing to tell to a random fellow who shows up with one of those identifiers (e.g. in large parts of Switzerland, unless you opt out, anyone can look up the address of the owner of a car with a given license plate).
Do you have websites that are attributable to you? Do they share analytics IDs/ads accounts/... with other websites that are also yours, but not easily attributable?