Now with 4K (or 8K!) displays it becomes completely credible to replace a white board with one. And the benefits of the shared whiteboard and presence is really solid when working with someone who isn't local.
The software infrastructure investment is immense however. And while I would love to see an open source version of this I doubt such a thing would ever exist. You need a video conferencing component, a drawing/archiving/sharing component, hardware that can accelerate the drawing function to avoid lag, and significant bandwidth to host both video and images being swapped updated in real time.