Interesting.  According to an article by Beresford (1957), common informers who made money from reporting misdeeds of fellow citizens to the legal system accounted for a substantial proportion of cases in economic law in the 16th and 17th Century England.  Bacon (1939) writes that this was also the case in the early American legal system.

Cited in Black (1973), The Mobilization of Law, Journal of Legal Studies, 130.