We often confuse the need for collaboration to obtain the best possible answer with the requirement of consensus.  In fact, these two things are completely different.  Collaboration is a process fo working together, of reaching out for the opinions, expertise and insight of others to achieve a better result than a single person could on their own.  It is the practical perspective of the cliché "two heads are better than one."  And I don't think anyone sees a downside associated with collaboration and leveraging the expertise of many to achieve a better result.  Collaboration tends to drive solutions to better.  Consensus, on the other hand, is a decision making methodology which by definition requires all to agree on the way forward, or at least not vehemently object.  Consensus often is characterized by compromise and even worse, the lowest common denominator principle which tends to sub-optimize solutioning.  Unfortunately too many people believe that by virtue of their input on collaboration on a problem or a solution also gives them decision making rights and the ability to veto a decision based upon the process of consensus.  This is a mistake that is often made and if organizations are going to make better decisions, streamline operations and be more efficient, they must be clear on the need for collaboration and the decision rights for the problem at hand (i.e. who makes the decision and how will it be made).  Collaboration does not equal consensus.

You don't make art by consensus.  Tracy Chapman

Indeed, scientific truth by consensus has had a uniformly bad history.  David Douglass

A consensus menas that everyone agrees to say collectively what no one believes individually.  Anonymous

To me consensus seems to be - the process of abandoning all beliefs, principles, values and policies in search of something in which no-one believes, but to which no-one objects. Margaret Thatcher