Horizontal leadership

The other day our department had a visitor who talked about the "horizontal leadership" in some social movement organizations. The basic idea, I guess, is that decision making is shared and that all members have ownership of decisions and input in discussions. I can see how this, in theory, makes people feel more vested in the outcome, how it is more inclusive than the traditional "vertical leadership" model, and why it has developed as an alternative to leadership models that have marginalized groups of people. BUT, I just don't get it. I guess I'm too old, too conventional, or too authoritarian. It seems like, in the end, someone needs to be "in charge." I am totally in favor of inclusive decision making, sharing responsibility, and consensus building. BUT, doesn't somebody, in the end, have to take the lead? Who communicates decisions to others in and out of the organization? With whom do those outside of the organization direct their comments and feedback? Is the lost efficiency worth it?