The majority of football arguments on here, for obvious reasons, tend to be between people who follow different sides. But pop onto pretty much any team-specific forum and you'll see fans of the same side bitchfighting over even the smallest points.
I guess you can answer in terms of age, race, nationality, class etc and that all of that might be interesting in itself, but I mean more in terms of what you think about certain players in the team, how the club is managed, what you want from the future, your opinion on footballing hot potatoes and so on.
I've recently taken a bit of a hammering on a Chelsea forum that I use from time to time and that, coupled with being disgusted by a Chelsea fanzine I read on a recent away trip, as made me acutely aware that I disagree pretty massively with many Chelsea supporters on stuff. It's not meant arrogantly (quite the opposite, really), but I'd guess I'm kind of a go-to guy for Chelsea opinions on here because there aren't many of us on DiS and I'm the most regular poster of the lot, but I'm definitely not the voice of Chelsea consensus ...