The task of proper anonymization is harder than it looks. Yet another example:
It turns out, though, that those redactions are possible to crack. That’s because the deposition—which you can read in full here—includes a complete alphabetized index of the redacted and unredacted words that appear in the document.We Cracked the Redactions in the Ghislaine Maxwell Deposition (via Schneier on Security)
This seems to be a corollary of Schneier’s Law: Any person can anonymize data in a way that he or she can’t imagine breaking it.
Although the truth is most don’t even try to break their own work.