I'm waiting for whiteboard sized touch screens to make their appearance. I know Microsoft was working on this a couple of years back.
No you aren't. You're waiting for them to come down from astronomical prices. You can get them now.
The problem may be that the mega screens are (from what I've seen) video quality, and thus crazy expensive. What's needed for simple whiteboarding, with the equivalent of dry erase "markers" for drawing, could be much lower in resolution and be limited to 256 colors. I really just want to be able to do what I can on a real whiteboard: draw some flow charts and diagrams, write text visible across the room and erase what needs to be changed.
Bonus for the digital version would be some straightforward copy/pasting (ie, move part of a diagram to a different place on the board), recording, and, of course, the remote collaboration aspect. (Any solution that involves a camera aimed at a real whiteboard is going to fail the "remote collaboration" aspect.)
In short, the video and audio conferencing stuff has already been solved, as has document sharing. So let that run in parallel on different systems and just solve the shared whiteboard problem.