Considering what a monumental pain in the ass it's apparently been for Blizzard to keep their servers running in the wake of Diablo III's launch and subsequent massive influx of players, it is perhaps no great surprise that other projects related to the game are suffering as a result. In this case, it's the real money auction house, a feature that was originally scheduled to go live on May 22, but now has been delayed for the foreseeable future.
According to a post on Blizzard's forums, the servers have generally been running smoothly since last night (and if my Twitter feed is to be believed, that's accurate). Still, the amount of manpower required to ensure those servers stay up evidently made the thought of launching the auction house next Monday unpalatable. Blizzard has no immediate timetable for when the auction house may finally go up, but promised to update players soon.
Elsewhere in Diablo III issue land, the same forum post acknowledges a bug where some players are either not receiving in-game achievements correctly, or not having them save between logins. The community manager who made the post said that Blizzard was looking into the issue, and would update as soon as possible.
Always online gaming, people. Wave of the future.