Interesting - Google released the Etherpad source code under an Apache open source license today. For those of you not following it, Etherpad is a 'collaborative' web-based text editor. It allows multiple people to work on the same document at the same time.
Here's the code:
http://code.google.com/p/etherpad/
The "Swedish Pirate Party" have a working demo of the code here:
http://piratepad.net/
I have no idea if it's possible, but it would be very interesting to create an extension to the Wysiwyg module that allows the use of the Etherpad source as the editor. If it was hooked in correctly, it would potentially bring collaborative real-time editing into Drupal.
Thoughts?