Some of you are grossly misinformed.
As Stuart mentioned, <Ensidia> downed the Lich King. Shorty after, they were temp banned for exploiting a bug. Blizzard did not release the LK on the ptr; they didn't have any extensive testing of the encounter. And, of course, the GMs didn't test the encounter as normal players because they don't have the skill that top guilds have. When Ensidia's rogue used Saronite Bombs in his rotation (like rogues should) it glitched the encounter and made it much easier. Ensidia knew something was wrong, but not what caused it. They did nothing wrong.
They should have had the achievement and loot removed, but not have been banned.