The amusing letter that Andrew cites below is an example of a broader political phenomenon. Stathis Kalyvas’ The Logic of Violence in Civil War has already become a classic of the field – among its many interesting arguments is an account of malicious denunciations.
the practice of denunciation exists to some extent in all organized societies, though it is really at home under authoritarianism … political actors are often surprised and overwhelmed by the response they receive when they solicit denunciations … However, what political actors take time to realize is that many denunciations are malicious, and a significant proportion false … Ordinary people are liable to ignore “moral self-sanctions” and engage in activities that further their self-interest but injure others even under everyday “normal” circumstances, but the immense majority stop short of homocidal violence. By exchanging violence for denunciations, political actors assume the considerable moral and practical costs of ridding people of their personal enemies … The study of the Duesseldorf Gestapo files by Reihard Mann shows that a plurality of cases was used to resolve private conflicts. … Denunciations between spouses (and ex-spouses) got so far out of hand in Nazi Germany that in 1941 the Gestapo headquarters in Berlin sent a letter to all local Gestapo posts in which they requested that special attention be paid to denunciations between relatives – particularly married couples. (quotes strung together from pp.338-347, missing out on a lot of detail).
Kalyvas suggests that denunciation should be scarce in highly developed societies with “atomized lives and anonymous relationships” – it is most likely in contexts where people resent each other, and even hate each other, but can’t easily get away from each other.