It seems Diablo 3 has been taken offline in Korea following reports of item duping. No estimate has been given by Blizzard Korea as to when the game will be brought back online.
This is a big deal.
Item dupes have plagued MMOs and action-RPGs since the dawn of the right-click. Essentially, usually using an arcane series of clicks and movements, players are able to replicate one item from another - repeatedly. What tends to follow is an economic crash as the value of in-game assets fall, followed by pain and drama.
What makes this doubly threatening for Diablo 3 is the real-money auction house - where players will be able to buy or sell items for real cash, swapping their bastard swords for bastard money. Throw the possibility of dupes into the pot, and you've got a nightmare scenario for players, Blizzard and their payment provider, Paypal.
Currently, the South-Korean version of Diablo 3 does not include the Real-Money-Auction house after it was deemed unacceptable by a local standards agency. Blizzard's Korean office was recently raided by the Korean Federal Trade commission investigating the refusal of Blizzard to refund customers over DRM issues. As Eurogamer report, no time-scale has been given for when the game will return online.
Here's the forum thread.
UPDATE: Here's a video of the purported dupe in action.