Blizzard's 3.3.5 patch for World of Warcraft went live yesterday, enabling the new Battle.net Real ID feature, allowing for cross-faction, cross-server, and when StarCraft II comes out, cross-game chat.
Real ID is a layer of friends list on top of the one World of Warcraft players are used to. Instead of tagging another character name as a friend, players can now tag the Battle.net ID of their friends, keeping in touch with them no matter where they are playing on the Battle.net network.
Say your guild is getting ready for a raid, but your healer is off playing StarCraft II. Not only will you be able to see what he or she is doing (should they allow it), you'll be able to drop them a line telling them to get their sorry ass in gear.
It also means that once you add a Real ID friend, you don't have to worry about adding all of their alts to your list as well. Real ID friends can even send out broadcast messages across their entire friend network, which sounds amazingly annoying, though perfect for dramatic "quitting the game" notices.
For those who'd rather have everyone known them as Porksword, the mighty Orc warrior, the Real ID feature is completely optional.
This is one of the first steps in integrating World of Warcraft with Battle.net, bringing players of all Blizzard games together in one big community.
Check out the Real ID page on Battle.net for more information on the feature, and visit the World of Warcraft patch notes page for more on patch 3.3.5, which also introduces the Ruby Sanctum raid dungeon.