Blizzard mentioned this new cross-game social aspect of Bnet at last year's BlizzCon. Real ID is an optional system for chatting with and keeping track of "real life" friends in any Battle.net game. You invite friends with your Real ID. If they accept, you can find out what game they are playing and on what realm and character. You can also chat across realms or games. You won't have to remember the usernames of your Real ID friends and family, because you will see their real names on the interface. And you will also be able to broadcast messages to all on your Real ID friends list, rather than just chatting one at a time.
I cannot wait for this to be implemented for WoW accounts. I would love to be able to chat with my friends who are scattered across many realms and who defect to play StarCraft. I really think this is great for more hardcore players (I'll be on my Alliance alt until you Hordies can get your act together for the raid) or very casual, chatty altoholics.
Will you use the Real ID system?