After a more thorough investigation, Blizzard discovers Exodus cheated on world first Hard Mode kill of Yogg-Saron:

"In our many attempts at trying to figure out a way to defeat Yogg zero watcher, we found a way to use bugged game mechanics to make phase 3 easier in zero watcher then one watcher. The bug is when someone is left inside the brain room of Yogg-Saron, they can still get aggro on the adds that spawn in phase 3. That means if you have someone getting healing aggro in the brain room, they will get aggro on the adds, which cause them to evade in place and allows for all of your raids dps to be focused on Yogg. We discovered this mechanic on a wipe, and decided to see if we could actually get it to work. The first attempt after that wipe, we realized it worked, and went with it and killed it on that attempt."

This Abuse of Game Mechanics brought them a 72 hours suspension, the Hall of Fame removal, and a quick hotfix of course:

"Immortal Guardians are now able to target players in the "illusion room" of Yogg-Saron with their summoning ability. This hotfix has been fully deployed to all regions. We're also in the process of deploying a hotfix for an issue with Immortal Guardians that could cause them to pause their movement before reaching melee range. This fix will also prevent the Immortal Guardian from running away if their target is stunned." 

http://forums.worldofwarcraft.com/thread.html?topicId=18031369918&sid=1