There's a music site called The Daily Swarm that has a weekly wrap-up titled
The Week In Hate. It covers Twitter wars between musicians (and sometimes the fans). So apparently Joel Zimmerman (a.k.a. Deadmau5) is pissed at Michael Buble over something that happened in 2010.
http://www.youtube.com/watch?feature=player_embedded&v=ZepEXg1EkaA#!Buble shakes hands and hi-fives people on the way to the stage. At the :08 second mark he starts walking towards someone but has second thoughts and continues towards the stage. I've watched this 20+ times and it gets funnier and funnier. The moment when Buble realizes that asshole in the mask is just trying to get on television is tremendous.
BONUS: Keep your eye on Zimmerman and you'll see him take off that ginormous mask and set it in the seat next to him.