I thought the next step for wikis to really make them have basically any kind of content and as much as is required would be to have an infinitely zoomable interface that anybody can draw on simultaneously. Links could be made by creating a lens to another portion of the whiteboard, and the idea was to have anything droppable onto the drawing area.
I got as far as making it zoomable by using the very nice Piccolo library for Java. Squiggles can be drawn anywhere at any zoom level. Although it's not quite infinitely large, it's effectively infinite, as in there is no need to really reach the limits. It would be nice to come up with a new API to get truly infinite functionality, however.
I made a test jar file kylewiki4.jar that implements squiggles. The rectangle button doesn't quite work. The left mouse button uses the tool (Pointer pans the screen, squiggle draws squiggles), and the right mouse button zooms when dragged left or right. It is kind of fun to draw something like the solar system, zoom into a planet and draw stuff, zoom in and draw a bit more detail, and stop once at the atomic level, and then zoom out slowly and watch things become larger and larger.