The involvement of fans of a football club can be enormous. I would like to give you two different examples.
First of all, in 2005 an American business family bought Football Club Manchester United. A lot of the fans of Manchester United did not like this, because they thought, the business men did not love the sport and the club, but only want to make money out of it. In November 2005 those fans started their own Football Club: FC United of Manchester. They play every week a match and around the 11,000 fans support this team nowadays, and to not support Manchester United anymore. As you can see, some consumers/fans used to be very loyal, but such a big change did change their idea about ‘their’ club as well.
Another example of the involvement of a football club and the fans is in Mexico. In Mexico there is a club in the second division where the fans make the squad. They vote before the weekend which players are playing and who it not. In the break the supporters can vote via Twitter, the website and text messages which players should be substituted. And believe it or not, they are doing very well in the league (fourth place). The players are very excited and say that the supporters always support them (because they make the line-up). Of course sometimes players are angry with the supporters because they do not play.
I think it is funny to see two very different ways with the involvement of supporters. One example: fans who were very involved left their club, and the other: fans just got more voice for the line-up and both parties, the players and the fans like it!