[I posted a version of this post in 2020 and 2024, but I've seen the problem enough since to think it was worth mentioning again.]
I have often run across documents written by lawyers that looked redacted—but all the supposedly secret information in them could be extracted with literally three keystrokes (ctrl-A, ctrl-C, ctrl-V). One was a court filing that was filed pursuant to a court order authorizing the redaction; but the material so carefully marked secret proved not to be secret at all.
Another carefully tried to hide the real name of a litigant whom the lawyer was trying to keep pseudonymous; but the name was one copy-and-paste away from being visible. What's more, when the documents were posted online in searchable spaces, search engines indexed the supposedly hidden material, so searching for the real name would find the document in which the lawyer had been trying to redact the name.
