Everyone's atwitter for Twitter. It's changing the game for how many people communicate. And the reason it's working is very similar to the reason Campfire works: Power is unleashed when you bring a simple UI to persistent real-time chat among groups.
Let's break down what we mean by that:
Persistent chat means people can leave and re-enter the discussion at any time and still participate. It's there for consumption whenever you're ready. It's "always on" yet can also recede in the background. It offers information when you want it but you can also tune it out when you don't want to be interrupted.
It's real-time. It happens now. Yet it also shifts time in a way too. You can "talk" without everyone having to stop what they're doing at exactly the same time. When you're ready, it's ready.
The group aspect lets you create your own inner circle. You choose who can see what. Open the doors to your friends and co-workers. Close them to the the outside world. Everyone's in the loop.
And don't forget the simple UI. You can get data in easily. There's just one field. You type and go. That means people actually use it.
Twitter and Campfire are clearly different animals. But fundamentally, they both get their strength from the same source.