I've seen so many refs fucking around it's not even funny. Guys going for take downs and landing on concrete floors because the ref was too busy looking at the other match. Last year someone got his arm broken because the ref was too busy talking with someone to jump in while the guy kept on cranking an arm bar...
Add a bit of bias calls and/or not knowing what's really going on and you've got some shit calls.
One way to win all your matches is to sub your opponents