Just consider Facebook (183 million active users worldwide) or Twitter (which at 4 million members has a smaller user base but which saw an explosive 752% growth in 2008) as indicators of the appeal of social media to consumers. What is most notable about the phenomenon of social media is that it represents not merely a new engagement channel, but a new conversation, one that takes the traditional brand-to-consumer dialogue and subordinates it to an emerging consumer-to-consumer dialogue. That shift makes this a whole new....