There's "Friends" and "Followers" and you can update your Twitter via a number of interfaces, including IM Clients, SMS messaging, and the web interface (amongst other similar connections). You can also get updates on such devices. I don't use any of these methods with regularity, though the concept of being able to update Twitter while waiting in line or something seems like a vaguely interesting use of normally wasted time.
I guess the idea is that if you and all your friends are on Twitter, you can keep up with what everyone's doing in one quick and easy place (the default way to read Twitter is with your posts and your friends' posts mixed together on one page). My problem: I don't think any of my friends would be into this. I suppose I could mess around on Twitter and find a bunch of folks that I'd want to keep up with for some reason, but that seems... strange. Why would I want to keep tabs on some stranger?
Jason Kottke claims that this is a huge time-saver and perfect for people who are really busy:
For people with little time, Twitter functions like an extremely stripped-down version of MySpace. Instead of customized pages, animated badges, custom music, top 8 friends, and all that crap, Twitter is just-the-facts-ma'am: where are my friends and what are they up to? ... Twitter seems to work equally well for busy people and not-busy people. It allows folks with little time to keep up with what their friends are up to without having to email and IM with them all day.I suppose this would be true, though I've been busy lately and have only managed to update Twitter once or twice a day. Naturally, there are some interesting side-projects like Twittervision, which shows updates happening in real time on a map, or Twitterverse, which shows common words and users.
It's an interesting and simple concept, and it could be useful, but I'm not sure how much I'll get into it... It seems like more of a novelty at this point. Anyone else use it?
Update: Some people are using Twitter for unintended uses, and there are some great ficticious Twitterers like Darth Vader. It's interesting how quickly people start pushing the boundries of new stuff like this and using it for things that were never intended.
Update 4.12.07: Aziz comments. He's using it to power a section of his sidebar, dedicated to songs... a pretty good idea, and using Twitter ("a device-agnostic messaging system," as he calls it) to power it is a good fit.
Oh, and it appears that my little flash badge doesn't really update (it does, but most browsers cache it and Flash won't update unless you clear your cache manually).