I'm not sure how well this will scale, but it's an interesting idea: while it's certainly possible to just create a Twitter account for your World of Warcraft characters (so anyone interested can always see what you're up to), the folks behind a new site called wowTwitter have gone a step further, and recreated Twitter's functionality specifically for Azeroth's virtual denizens. It's very barebones right now, but basically, after you register, you can punch in any of your characters, "verify" them by changing something about them in the Armory (like unequipping the piece of gear on your wrist), and then you can send and receive messages on that character, with special channels created for the guild, your realm, and so on. I thought it used Twitter somehow, but it seems completely separate: they're running their own database and servers, so while the two work the same way (there are "@" replies and hashtags), they don't interact at all.
Which means they'll also have all of the problems that Twitter has had -- when only a few people are using your database, it runs fine, but if it starts to scale up at all, then you run into lots of "Fail Whale" downtime. And I'm not sure we need a whole other system just for WoW characters (though this one does have the nice bonus of "claiming" your character so it can't get impersonated). At any rate, they're in beta right now, and actually hosting a cash money prize contest for the most characters verified and tweets posted, so a link from us will probably show them how ready their system is. If it's your thing, go forth and wowTweet!