More support for using visuals
I agree that we need to move towards visuals that are relevant and easy to understand. As I have been saying for a while now, all we need to do is look back 5,000 years to see how humans communicated back then. We drew something on the cave wall and we told a story. It was effective back then and is effective today.
While I agree that being more visual is communicating more effectively, I would suggest that since most of us will have to still present our information using PowerPoint or distribute it via e-mail or the web, we will still want to get our visuals into electronic format. The back of a napkin is a good analogy, but perhaps not to be taken literally.
If you are not a great freehand artist - I know I am not - then using the simple tools in PowerPoint will serve you well. They make sure your squares look square and your lines go where they are supposed to go. And you can erase any mistakes easily.
Just make sure you have simplified your concept before you start - whether using PowerPoint's drawing tools or the back of a napkin. It is the simplification of the concept and focusing on the key point that will be most important for your audience, not necessarily the format you use.