You've heard of many companies working on Paper-like displays, but there are some working on Paper-based displays!
November saw news from Acreo (A Swedish company) on their work on Organic Electronics on Paper (or Paper-like) substrates.
They have combined the basic electronic work (conductors, transistors etc) with an ElectroChromic display (segmented display at the moment, although they talk about matrix bitmap displays for the future) to build a display on paper.
It's OK contrast, low-voltage, pretty slow (1 second) and of limited bi-stability (10-15minutes).
I don't see any particular need for paper to be the substrate, or particular advantage in it for the performance of the display except it's cheap, white, used to being viewed or read from, biodegradable and available in abundance in Sweden! :-)
Most of their new work is based on their high-speed roll-to-roll printing/manufacturing processes.
If you want to understand their work in this area more (and see their "system on a sheet of paper" demo and other interesting areas) then here is the (direct link to PDF file) Acro Aperturen Newsletter that describes their work.
For previous and newer newsletters from Acro you can consult them in PDF or HTML at Acreo's Aperturen Newsletters home page.
Anyway, fun stuff!