People can't react to ideas that are not modeled or simulated for them - it's simply too hard to get everyone to "think" the same way. Place a prototype or simulation in front of them, however, and the reactions are worth their weight in gold. The speed to prototype is important because it helps highlight the "gap" between idea generation and the resulting next steps. A long gap indicates that your firm does not have the processes and systems necessary to bridge the gap, and will probably be beaten to the market fairly frequently. A short gap can actually increase cycle times but improve the product, as a rapid prototype receives a lot more commentary and feedback into the system.Interestingly, he maintains that taking a long time to put a prototype in front of a customer indicates your product will probably fail in the marketplace - not just because it won't realize the benefits of feedback, but because it reflects an organization not conducive to successful product development.