Why are some regular season college basketball games called Bracket Busters?

BracketBuster games are set up by ESPN between teams in different "mid-major" conferences. Basically, it is ESPN trying to get some exposure to some of the smaller colleges just before NCAA tournament time. However, only a few of the teams playing in a BracketBuster game are truly in contention for a spot in the tournament. They are non-conference games played at a time where most conferences are only playing in-conference games. It is generally one of the most exciting games of the year for smaller schools, especially those in contention for the NCAA tournament. Also, some of the games are televised on ESPN.

Also comes from teams that get into the tournament and upset higher seeded teams. They 'busted" the brackets for everybody. So now they have these games in the middle of the year with "mid-major" teams playing each other. Usually teams they think will pull an upset this year(Winthrop, Mo. St. etc.)

A not so good team defeats a another that is looking to playing in the NCAA tournament. That loss for the better team can knock them out of going to the tournament.

Also, a team that normally would not go to the tournament, pulls off an upset win and gets them in the tournament and knocking out another that maybe should have gone.

The Bracket Buster refers to a specific weekend in which the "mid-majors", looking to enhance their position on the bubble by strengthening their RPI and SOS, arrange to play each other. It is a collective effort by the mid-majors to get extra at large bids from the BCS conferences.