In an update to the game's official FAQ, Blizzard have detailed new "Global Play" functionality for Diablo III that will allow players from any region to get their game on outside of their home servers.

The three regions are defined as The Americas (which includes Australia and New Zealand for proximity reasons), Europe and Asia and players will be able to hook up with others outside of their region, with a few caveats:

• While you can access the gold-based auction house in any region in which you’re currently playing, the real-money auction house is only available in your “home” game region -- you can only access it for the characters you have in your “home” region, and you cannot use the real-money auction houses in other regions. Note that players in some regions do not have access to a real-money auction house at launch.
  
• Heroes, items, and friends lists do not transfer across regions.
  
• Players are subject to the policies in their selected play region.

Personally, we'd still prefer if it wasn't region-restricted at all, but at least there's an option now.

Hit up the complete FAQ for a much more detailed overview of the Global Play functionality.

Diablo III is coming to PC and Mac on May 15th 2012.