Blizzard has just announced that players of Diablo III the world over will be able to join and play the game cooperatively with each other thanks to the new region-free servers that the company is implementing upon the game's launch.
With Global Play, Battle.net will be split into three general regions:
The Americas – For players in the US, Canada, Latin America, Australia, New Zealand, and Southeast Asia.
Europe – For players in the European Union, Eastern Europe, Russia, Africa, and Middle Eastern countries such as Israel and the United Arab Emirates.
Asia – For players in South Korea and the regions of Taiwan, Hong Kong, and Macau.
The characters you create will reside and play in your "home" region, which is determined by where you bought your copy of Diablo III. You can then hop onto the Global Play option to switch to any of the other regions, so players in America will, for instance, be able to play with their friends in Germany, Korea, or Japan.
Unfortunately, the characters you create and the items you earn will be limited to those regions alone. In other words, you won't be able to bring the character you have on the American server over to play with your European friends. You'll have to create a new character on the European region for that. Additionally, you won't have access to the real-money auction house on a foreign server, for obvious security reasons.
It's not perfect, but it's much better than the region locking of Starcraft II or any other game.