Check out this fascinating demo of Siftables at the TED conference from David Merrill. There’s more on the Siftables project website at MIT.
I’m not sure how you’d do something like compose a document or check emails on them. At a time when computer monitors and resolutions are growing, it does seem odd to have tiny bits of information again–smaller than a cell phone, really.
The interesting thing about them, though, is the usability and the apparent user experience. It’s very “natural” and “intuitive” (whatever those terms may really mean).