I came across this article in A List Apart that really sums up the positives of working with web prototypes. David Verba keeps the prototype design on center stage where it belongs. Here’s a taste of what he has to say…

Prototypes keep us focused on our actual goal. I’ve seen countless hours spent generating thousands of pages of documentation that were never used. This in itself wouldn’t be so undesirable if we had infinite developer resources. Unfortunately, this is rarely the case, and I’ve often seen features cut from a product launch in favor of generating “better” documentation. With prototypes, the focus is always on the application and making it better, and it’s much easier to stay focused on value to the end user.