The Diablo III Auction House is still down after a gold duplicating bug was discovered after the patch went live.
After Blizzard-Activision patched Diablo III to version 1.0.8, players quickly discovered an economy destroying bug that resulted in the duplication of gold on a massive scale. Blizzard then had a choice to make. Do they roll back the servers and make their players angry at their lost progress and lost loot? Or, do they try to handle the gold dupers one at a time? Unfortunately, Blizzard-Activitision went with choice B and have now closed the Auction House much longer than they initially reported in order to track down and properly punish all those who duped.
The duplication bug, it seems, is the result of a mathematical problem within the coding of Diablo III itself. To put things simply, you could make 4,294,967,296 gold for 1,705,032,704 gold by creating an auction of 6,000,000,000 gold and then cancelling it. The reason these amounts are so specific is that the way Diablo III's auction house stored the values is a bug in the way that Diablo III's auction house was programmed
This dupe spread quickly throughout the community and within a few hours, the amount of gold in the economy was enormous. While Blizzard made the decision to deal with each duper individually, it may end up becoming a more wide-spread ban than the initial wave of Day Z bans last year.
Source: Diablo III Forums