Other reasons:
The return of Spartacus from 08, except resulting in the "death" of BD's drum major and leaving no one able to conduct the remainder of the show, causing havoc.
Chuck Norris forbids it.
Member in crowd shines laser beam at mirrors, causing inability to see.
And finally, tensions arise in the corps, due to an incident that can only be alluded to by the words "And one time, at band camp..."
As a side note, it would be cool to see Cavs "assassinate their dm " with the rifles as a finals surprise.