Sean Bluestone of A List of Lists blog wrote an interesting article about the 5 largest gangs in the world. For example, take Japan's Yakuza:
Popularized in the west in several movies, Yubitsume is the cutting off of a finger as an act of apology or humility. For a first offense the offender cuts off the tip of his left pinky, giving it to his boss. Sometimes an underboss does this to his boss in order to spare a member of his own gang from retribution. This is so prominent in Japan that when UK kids shows Bob The Building and Postman Pat were imported, the Japanese considered adding an extra finger to the characters’ four fingered hands to avoid scaring children.