I agree soccerboy, the fans being on one side of the field makes for a more exciting environment. Even with (relatively) large numbers of fans for both teams, having them sit on opposite sides takes away from the drama. Consider this: lets imagine that each team's supporters are solid energetic entities, kind of like magnets. The closer they are together, the stronger the force between them (see Newton's law of universal gravitation). More force=more intensity=better game
