If leadership is required, then it needs to be assigned by someone and not given to the loudest/most talkative/strongest personality. It needs to go to the person best able to consider all points of view and make a decision. I've been in "forced collaboration" projects that were anything but collaborative. Our group was to reach some decision that would affect an entire department. All opinions, thoughts, etc...were expressed during many meetings, but then the conversation started "circling back". At that point, a manager stepped in and appointed a leader to take everything into account and arrive at a conclusion. Had a leader not been appointed, we'd still be going in circles.
I've also worked in a truly collaborative fashion where no leaders were necessary. Everyone brought a unique aspect to the situation and, putting all the pieces together, we were able to reach agreement. It's a thing of beauty when that happens.