Cool stuff! I've looked a bit at what it uses: shapes drawn are vectors, the app uses Raphael ( http://raphaeljs.com/ ) for drawing, and Pusher ( http://pusher.com/ ) for whiteboard syncing.
Regarding the Pusher web site, am I the only one who cannot resist the temptation of loading up Firebug to verify whether the counter is for real or "interpolated"?
It currently starts approximately at 14,230,617,000