Football clubs are organized like corporations. They collect funds from their season pass holders (socios), and in turn these socios have the right to vote on the principal decisions of the club. The dynamic is very similar to that of shareholders in a company.
The main difference is that investors can buy more than one share in a company, whereas a football fan is usually only a socio for himself. That would seem to imply that all socios have equal influence. Not true. In big and important football clubs, there are a group of socios who have tremendous power and influence. In Argentina, they're known as the barras bravas.
The barras bravas are the violent sector of the football club's fans. They are the ones who yell vulgar insults, or the ones who beat up the other team's fans after losing a match, or the ones who place bullets in the front seat of the players' cars after a poor performance. The barras bravas are especially notorious for their practice of cuidacoches, which involves extorting money out of people who park their cars at the stadium so that they can "take care of their cars" (i.e. have them not steal it).
Among the barras bravas, there are one or two leaders (never more, for reasons we will see later), who are probably the most powerful figures in the club. Their power stems from their ability to round up large numbers of votes among the barras bravas, either because they are charismatic, or because they are well-known in the neighborhood, or because they have a lot of contacts through trafficking goods. As a result, even if the leader just has one vote himself, through this process of rounding up votes he effectively makes himself a majority stakeholder.
The leader of the barras bravas is a key player in the internal politics of the club. For example, if the club hires a technical director that the other directors don't like, they can have the leader move the barras bravas against the technical director and get him ousted. The president himself can encourage the leader to have the barras bravas put bullets in the players' cars during practice if they don't perform well.
To keep the leaders of the barras bravas on their side, the presidents of football clubs buy them off: all-expenses paid travel with the team; access to all practices; 300 tickets, to be sold at 30x the retail price—being the leader of the barras bravas is clearly a lucrative business. There is a reason, though, why the barras bravas only ever have a few leaders at a time: there is so much money and power at stake that the leaders use any means necessary to maintain their position. Threats, blackmail, and murder are all part of the gig.
The grass of la cancha is so clean and immaculate. It betrays nothing about the people who work to put the spectacle together.