Imagine being at a trade show and having a customer come up to you and ask a question that is completely out of your area of expertise. So far in fact that you're not even sure who to ask, or where to ask it. If you were in a large room of varied experts you'd just call out and hope that your request reached someone.
The idea behind the IBM Community Tools client was to prototype the idea of broadcast messaging -- sending messages out to large groups of people and letting them filter out messages that they are not interested in. By default, users of the tool would send messages to a specific channel, or to "everyone".
More information behind our experience with people using the broadcast messaging tools can be found in the ACM Queue article - Messaging to the Masses
The broadcast client was written as a plug-in to a larger framework, all written in Java using the SWT library from the Eclipse project for a native platform look and feel.