At least one good friend of mine regularly uses Twitter - I know because he integrated it with his Facebook account so I see it there, plus as a sidebar on his blog. I never really understood the point, but on Wednesday night I was listening to all tech considered and heard a great short piece about some people using a private application of the same idea: yammer.
What I remember is basically:
(I'm paraphrasing now) "Email is old, yucky technology. Its fine for one-0n-one communications (although there are better options here too). You have to spend too much time figuring out who to address, what order to list people in for your addresses lists, and people talk too much (like this blog I bet you're thinking)". Twitter's great, but if you have private things you want to share (trade secrets, etc.) its public nature is a deal-killer. So - companies get a private twitter - yammer. When you have a question, ask the group. The first person to reply will let everyone know. Likely someone else will benefit, and time has been optimized. People originally feared that employees would waste too much time if given access to this technology, but experience has shown that while there are some abusers, the advantages WAY outshine the potential troubles.
I'm sure we'll see lots more of this style of communication - both among each other and with technologically connected patrons.