Described as a rare, inverse form of crime. According to Reaper Man, an anti-crime must:
... be done in such a way that it causes outrage and/or humiliation to the victim. Merely giving someone something is not enough. Examples of this type include breaking-and-decorating, proffering-with-intent, and whitemailing (for example threatening to reveal a mobster's donations to charity).
Even on the Discworld, anti-crime has never really caught on