It's often easy to forget that virtual stuff, is well, virtual. Intangible. Building a prototype for your idea is cool. Using a drawing program to make flow diagrams is fine. But often doing it on paper (or whiteboard) is better. For one, it's tangible. Unconsciously, we register it as something "real" more easily. Also, it's very visible and collaborative. Human interaction! And unless you're a god of the mouse or trackpad, using a pen will often be faster to sketch things out. Finally, when your entire team is hitting the keyboard, getting a piece of paper out is a sure way to bring in attention, and, somewhat, bring everyone closer.