Squarely in the “because you can” category: YouDisco is a research project at New York’s Eyebeam that simultaneously streams up to eight YouTube videos onto a rotating virtual disco ball. Frame rate is … well, impressive given what it’s doing. The project is the work of Jennifer Jacobs at Eyebeam “with the help of Jeff Crouse.”
What is interesting about this is that you do get interesting effects on a computer screen when you leave 4:3 rectangles behind, just as in projection.
Along the same lines, though focused on a mash-up of two videos side by side (sometimes to hilarious effect):
http://www.youtubedoubler.com/ (which is, for me, playing Shatner yelling “Kahn!”)
Lots of interesting graffiti and motion and illustration work on Jennifer’s blog, like this piece: