MMA is a dangerous sport as it is but when you factor in a trick cage door things get all the more interesting. Makes a fighter want to spend more time throwing punches in the center of the octagon and less time grappling against the cage. When you think about it, this could be a brilliant accident. Unexpected trap doors are always a crowd pleaser. Imagine for a second how awesome this would've been if one guy kicked the other in the chest and sent him flying through the door. Now that's entertainment. 1:27 mark is what you came for.
Note: According to Cagewriter, both fighters were compensated as if they won and each walked away for the incident under their own power.