A more convincing hypothesis is that overseeing a large population of itinerant drivers following unpredictable routes may be too complex and expensive a chore for any central agent to have an interest in acting as guarantor. Likewise, drivers would be reluctant to pay someone other than themselves to do the enforcing, since policing can be efficiently conducted only by drivers themselves as they travel at random through the city, each one representing a potential threat to all the others.

Diego Gambetta, The Sicilian Mafia The Busi…, loc. 601