While there, I observed a lot of projects where I was literally working with a room full of world-class people - folks who had given TED talks, folks who had started major open-source projects, folks who had written the "Bible" of their particular subfield of computing - and the final design we came up with was worse than what any one person in the room, working on their own, could've come up with. Good designs tend to be both controversial and coherent: they take a position, not everyone agrees with the position, but they do it anyway because self-consistency has its own benefits that are often intangible but highly valued by users. When you design by compromise, you end up sanding off all the most innovative (= hard to communicate) parts of the design, and end up with only the bare minimum that everyone can agree on.

It's interesting that when you put a bunch of average people in a group, have them independently make a prediction, and then average the predictions, you end up with a result more accurate than any one participant's prediction. When you put a bunch of really smart people in a group, have them cooperate to make a design, and look at the design, you end up with a design that's worse than any one expert's original design.