Twitter can be a pretty public communication tool, which is okay for journalistic purposes when you are trying to reach a large group of readers.
But what if you want to restrict the group? For instance, what if you want set up a premium service with specialized content? Or even just set up a staff communication tool using Twitter? Or how about a replacement for something like the JACC faculty listserve?
Mashable, the social networking blog, has reviewed a number of Twitter add-ons that would let you set up such private groups.