This proposal made it onto one of the GNOME devel lists. It's for desktop tape, which is:
A desktop Tape would homogenise multiple desktops into one whole: rather than moving from screen to screen, you move smoothly along a long, 'infinite' horizontal space, like several screens glued on to eachother; or, like a long tape.A simple idea, but still fundamentally different than it's nearby neighbors, the virtual desktops. I'd be interesting in giving this a try or seeing it implemented. I'd have to use it a bit before I'm sold though :)