Combine the power that word of mouth has over the credibility of a message, and the unprecedented efficiency and reach of interpersonal communications today, and its perhaps no surprise that whole markets seem to be able to talk themselves up and then down at scales that stun even the experts.  David MacGregor refers to the concept of "informational social influence", or groupthink, under the influence of media that accelerates the message. Alan Bollard is doing his best to be a calming influence, as are other free thinkers, however, bad news is good copy and travels faster so we may yet be a victim of our own heard mentality.