Upon visiting Blizzards Battle.net today visitors will be greeted with the news of the all new Centralised Account.

The new Centralised Account System allows you to unify all your existing and future Blizzard game accounts, including multiple World of Warcraft accounts.

What are the benefits of creating and using a Battle.net Account?
The new Battle.net Account allows you to log in to World of Warcraft, manage purchases at the online Blizzard Store, keep track of CD keys for your Blizzard Entertainment games, access our websites (such as the World of Warcraft Armory), opt in to upcoming beta tests, and more using a single login -- just your email address and a password. In the future, we plan to add more features, including tools to make it easier for friends to communicate between games and to help bring our community of players closer together.

Blizzard plan on making the system mandatory for WoW and all future Blizzard releases but for now the system is entirely optional. As Blizzard builds additional functionality to the system however all WoW players will need to migrate in order to continue playing.

Being built from the ground up as a new system for WoW and future Blizzard releases means that it is incompatible with Diablo II, Starcraft and Warcraft III. In order to play these games you must login with your original account which has been renamed Battle.net Classic.

Source: Battle.net