One of the most difficult things to evaluate in college basketball is individual defense. Defense is more team-oriented than offense, and even in 2007, stats for measuring individual defense are primitive.
An exception to this difficulty, though, is the dominant big man. Typically, the nation's best shot blocker also is considered the nation's best defender, and the impact on his team's defense is more obvious. Since blocked shots are kept as an official statistic, we can have some idea of how dominant a shot blocker is, even if we can't see most of his team's games.
However, to understand any stat, we need some context. Unfortunately, blocks per game has very little context associated with it. But thanks to the detailed record keeping that is beginning to become available at the college level, we can put the performance of shot blockers under the statistical microscope to reveal which ones are truly superior defenders.