Lately, I've been thinking alot about online collaborative authoring processes and have designed an experimental platform to explore some thoughts on this through drawing. 

Draw Rabby is a multi-authored, dynamic, visual story-telling platform.  At Draw Rabby (https://drawrabby2.tumblr.com) you are invited to draw on a shared canvas, responding to or in some way interacting with the other drawings present. Feel free to start anywhere - add a line or a complete sketch, as you wish. Your drawing saves automatically. The canvas is refreshed periodically to enable a new drawing sequence. The dynamic stories created on  are periodically recorded and stored in a permanent collection on his sister blog, Drew Rabby (http://drewrabby.tumblr.com/).