Divorce disputes. Barbra Streisand effect lawsuits. Legal battles that deal with minors, pornography, and libel. State secrets. Proscribed speech in countries where naziism or holocaust denial are illegal. Trade secrets. Military secrets. Espionage.
Basically, whatever the elite Judges and Courts can think up and order people around to do. If those courts are tried to a military dictatorship, then the will of the State, which leads to debtors prison and other nasty things. If the courts are tied to a police state, then the police can be ordered to lock people up until the content is removed or the prison sentence is served.
The MPAA is notorious for making it illegal to share keys and/or share info on how to bypass video encryption schemes.