When I read some of the early posts about the various Occupy Wall Street groups, I cringed when I saw the phrase "voted by consensus". So I thought I would offer some clarification:
People who are new to the consensus decision-making process often confuse it with some sort of voting process in which everyone has to vote the same way, that is, to express the same preference. But the proper name for this is "unanimous voting" or "unanimity". It is very difficult to achieve unanimity and it occurs only rarely in groups with more than one member. If you force a group to make decisions by unanimous vote, chances are good that the group will never do anything or that a lot of people will be coerced into doing stuff they actually think is a bad idea. And then the group will likely deteriorate very quickly.
The key word in the consensus process is consent. When you vote for something you are simply expressing a preference for it, and when you vote against something, you are simply expressing disagreement with it. But when you consent, you agree to the decision of the group, even if you still disagree with it somewhat. If you refuse to consent, you are saying that you disagree enough that you will prevent the group from moving forward.
The point of the consensus process is to create a safe place where people can honestly and thoroughly discuss issues and then generate real solutions that address the concerns that people raise so that when it comes time to decide, everyone can honestly say that they agree that the proposed solution is the best one for the group. That doesn't mean that everyone thinks the solution is great or doesn't have some problem with it. It just means that it is a better solution than doing nothing and better than doing any of the other things the group might actually agree to do. So everyone consents to that better decision. Note that you can consent to things in one group in one particular situation (such as during an emergency) even though you might not consent in a different group or in a different circumstance.
Again, you are consenting because you know from the thorough discussion that this is the best decision for the group at this time and place.
Every day you probably consent to things that you disagree with: you consent to working at a shitty company because you need the paycheck they give you; you consent to paying a horrible corporation because you need the food or electricity or internet access that they provide in exchange. You may agree to let a group make a decision based on the preferences of a majority of the people present (governance by majority vote).
But sometimes you have to refuse to consent: to say "No, I won't allow this anymore." Nonviolent struggle — strikes, boycotts, blockades, etc. — is all about refusing to give your consent to things that are unacceptable.
Also, consensus is a process for people who want to work together honestly in good faith to find good solutions for the group. It cannot really be used by people who do not, can not, or will not cooperate. Consensus should not be attempted in a group with people who want to dominate or control others or who want to maintain their privileges at the expense of others. In these situations, nonviolent struggle is a more appropriate process.
Knowing when to consent and when not to is difficult, but the more you practice democracy, the better you get at it. Keep struggling and snuggling.
For more, see Consensus is Not Unanimity, other resources at the Vernal Education Project, and resources at Organizing for Power.