Simple websites are easy to use, easy to understand, and nice to look at. In my opinion most websites are filled with too many complicated ideas and have way too many paths / options available to the user. To me, any path that leads the user away from the goal is a distraction and should be depreciated.
What seems to happen during the collaborative stages of development is that many ideas are added to the original set of ideas. It would seem that a website featuring many great ideas would be a great website. If well executed, a collaboration of great ideas can (in some cases) become a great website. On the other hand, projects featuring too many ideas often turn out confusing and not as effective as the simple ones.
Heres an example:
Lets say you needed to get to a friends house for a BBQ. He lives all the way across town and you need to be there in an hour. I would probably prefer to get one set of directions and probably from mapquest.
Another approach would be to call some friends and get some opinions on how they would navigate across town. Who knows maybe somebody knows a shortcut? Or a route thats more scenic? Is there road construction? Wait, maybe I should call Steve, he grew up in that area. By the time your done with this approach, the chances of getting lost on the way to the BBQ are tripled.
I know this example doesnt necessarily apply to webdesign and the collaborative process but I think it helps my point.
Simplicity as a result of a creative process is "the ultimate sophistication", as Leonardo da Vinci said. Achieving simplicity is a difficult task, especially in webdesign. Here you have designers with one set of opinions, clients with another, technologists add another twist. Then to top it all off - SEO plays a factor.
In order to make sure your website is effective, its important to identify the goal of the site and make sure that goal doesnt become depreciated.