I finally got a chance to look at the IBM Research history flow site, which is described as: "visualizing dynamic, evolving documents and the interactions of multiple collaborating authors: a preliminary report".

I saw a number of the document history flow images posted on different blogs and didn't immediately get too excited by them, but reading about what the images represent makes it more exciting, in particular as a way of picturing collaboration. The IBM folks use Wikipedia for their source examples of collaborative documents, and that makes for some interesting pictures.