What's a Bacon Number?

Gbradley has discovered why you don't want to play Six Degrees of Kevin Bacon with anyone from The University of Virginia. It seems that they've taken the fun out of it (like good engineers) and created a database linking actors by movie to Kevin Bacon.

I'm not sure exactly how the game is played, but I think you would want to research anyone with an infinite Bacon number if you were to consider trying the game.