I'm not sure I understand Twitter all that well. Even the makers of Twitter don't pretend to understand Twitter all that well.
Twitter's great for someone like me. Someone who doesn't, can't, won't and prefers not to have a real person to talk to. I've been using Twitter for over a year and a half, and now, it's become almost indispensable, given the way I operate.
In a lot of ways, Twitter is like Dumbledore's pensieve to me. Sometimes I just get overwhelmed with all the things I end up carrying in my head. During these heated times, I simply write a short note about it on twitter, "favorite" it (i.e. star it), and then come back to it later. This may not sound as useful at first, but when your head is brimming with tens of hundreds of threads, things start to feel very uneasy.
I'm sure you've experienced this phenomenon one too many times yourself. The thing is that most people respond by stressing out. I, on the other hand, just write them down and forget about them for a while. This ensures I tackle things one at a time, and never all at once.
Sure I can always maintain a text file for that sort of stuff, but I know if I did, I'd end up writing paragraphs on it and then it'll end up becoming a blog post like this one you're reading. There's something about the 140 character limit that is very limiting, and yet very exhilarating.
At the end of the day, I feel Twitter scratches a very legitimate need of mine. I don't know if it scratches any need of yours. That's for you to decide. But if it does, you should start taking fullest advantage of it, if you aren't already.
But whatever you do, don't assume you understand Twitter. Because the truth is, no one does. You will never understand people's motivation for using it, certainly not mine. Just treat it like a black box. Like a fruit whose juice is waiting to be extracted.
My twitter page: http://twitter.com/meetrajesh