Even before social media and the Internet were glimmers in Al Gore's eye, "word-of-mouth marketing" was important to brands. That's because people have had conversations about brands since the dawn of time. I still remember, when I worked at a sporting-goods store in high school, my manager telling me that a customer will tell two people about a positive shopping experience but will tell seven people about a bad one. I can't say how valid those numbers are, but the gist rings true: Conversations between consumers about brands are far more influential than any advertisement has been or ever will be...