All A-Twitter-y

So I signed up for Twitter a week or so ago, mostly out of geek-guilt. This is the new hot thing, right? (Or, more likely, the old hot thing by this point.) So I figured I should do something with it.

But the actual "doing something" has been harder to grasp; I haven't actually twittered yet, nor am I entirely sure what I should twitter. (Is it really just "OK, now I'm in a cab." "I paid the driver, and I'm in front of the building." Oh shit, it's raining." "My hair is horrible!" ? Just a random string of whatever the person is doing at the moment? Why would anyone who isn't fourteen care?)

Today, someone actually signed up to follow me on Twitter, which is faintly ominous. (Why do social networking sites lend themselves to terms that imply uncomfortable things? All this talk of "friends" and "following" and "sharing" makes the Internet sound like one big EST encounter group, circa 1975.)

And now I feel like I need to Twitter something, because now someone's following me.

Has anyone out there used Twitter, and actually found it useful. If so...for what?