I have to say, I've tried a digital whiteboard (Samsung Flip), and that thing was very cool. Wiping it (starting a new page) automatically saved the last into a history roll, and you could send them over email/network drive/etc. We made a draft design of a feature, then started a shared document from the uploaded picture made on the whiteboard. Worked quite well.

The main problem is the price, we can hardly afford one for each person, especially since it's not exactly something we use daily. Plus, even if we did, I'm not sure there's anyway to sync them in real-time.