With the expansion of Nebraska to the Big 10, in order to allow a championship game, the conference had to split into two divisions:
Division 1: Michigan, Nebraska, Iowa, Michigan State, Northwestern, Minnesota
Division 2: Ohio State, Penn State, Wisconsin, Purdue, Indiana, Illinois
(For some background and additional analysis of this issue see:
Adam Rittenberg at ESPN says that the divisional alignment was based on economics, in particular having a marketable championship game and ignored tradition. I agree with that.
I think one of the big appeals of sports is rivalries. Since sports are a zero-sum game, you cannot increase interest by increasing the average number of wins. Rivalries can make certain games matter more and thus increase the entire "interest" pie. To develop rivalries you can depend on:
1. Tradition. The easiest way is to have traditional rivals already in place.
2. Geographical proximity. Having two teams near each other increases interest in a particular game since the opposing fans might travel to the games or interact with opposing fans on a regular basis.
3. Big or competitive games. Think Cowboys-49ers or more recently Colts-Patriots. In the Big 10 a good example might be Penn St.-Iowa in recent years.
I think the Big 10 really dropped the ball in not keeping some of their rivalries intact. Wisconsin is not in the same division as what I would assume to be their three biggest rivals: Minnesota, Iowa and Michigan and will only keep their rivalry game with Minnesota (each team has one rival in the other division). Penn St. and Michigan St. are not in the same division. Even the recently developed Penn St.-Iowa game is no more.
In Part II, I will discuss the issue of geography.