I spent twenty minutes trying to remember the name of this brilliant, unmoderated, real-time, infinitely-large canvas of collaborative and anti-collaborative text. It’s Your World of Text by Andrew Badr.
If you run out of room, you can scroll to a fresh plot of page à la Google Maps.
Even more brilliant, Andrew released the source a while back. Interesting to see that it’s built on Django, and that clients keep sync by polling the server instead of some kind of pushed data from the server via Comet or a hidden socket.