> I still don't get the value of twitter
"Talk directly to semi-famous people" is one of the chief value propositions.
Suppose you are a fan of some public figure - say, an actor or a politician who has more than thousands of fan - snd you want to ask that person a question or give them a compliment.
If they're on twitter, there is a pretty good chance you could get through and have that person actually read what you have to say. If you're sufficiently witty and relevant it might even turn into a conversation. There is no other medium for which your chance of getting through is that large, and part of the reason why this is true is due to that 140-character limit.
Consider the unread messages in your email inbox. Any single email you open might turn out to be a quick topical one-liner, carefully edited to make a single point clearly and say nothing extraneous...but it's much more likely to be rambling and poorly edited. In the worst case, it could take an hour to read and understand a single email. So sorting through email (or any other non-bounded message stream) is daunting and best delegated to somebody else if you get too much of it.
The fact that tweets have to be so short forces tweeters to think carefully about what they want to say and to make their point quickly. If the message is a compliment or comment, it has to be an efficient one. If it's a question, it's an efficient question - you don't have to skim past a page of introductions and compliments and caveats to find it. And if the text is ugly or pointless or hateful, you can "block" the sender after you see a mere 140 characters of what he has to say.
So that's one use case - talking directly to people who otherwise would be protected by a circle of PR flacks. You can currently do that more effectively on twitter than most other services.
Even when talking to non-famous people, the 140-character limit imposes discipline that can make conversations more fun and efficient, but it only makes sense if some critical mass of the sort of people you like to talk to and hear from are already on the service, so it might not make sense for you yet. That's essentially a bootstrapping problem.