A recent article from the Harvard Business School titled, "Encouraging Dissent in Decision-Making," points out the value of speaking up (and leaders being able to listen up). I agree with much of what the article states -- I can't count how many times the loudest opinion can squash a great idea. The best ideas can come from the places you least expect it. An optimal situation is to set up a forum for ideas to germinate (and ensure everyone loses their egos at the door). Group dynamics are only possible when the leader or manager is a participant in the session (be it brainstorming, ideation, or a discussion).
By using great examples throughout history, the article makes some clear points. The articles states: "History shows that the best and the brightest--the smartest guys in the room--often make mistakes because they won't listen to what they falsely believe is not worth hearing. Shutting out voices that might say otherwise can be risky. Decisions are seldom better for silence, and overcoming that is a key task for the leader of any organization."
Read more on the HBS website.