Relevance has long been a central tenet of effective advertising, but the rise of Facebook and Twitter are forcing a redefinition of the term. As it turns out, many people in social networks don’t want to talk about your product, they just want to talk. We’ve long known that inserting brands into social-media channels requires a conversational touch, but many are surprised by just how conversational. There’s increasing evidence that the most-effective kinds of marketing communications on these websites are simple, random, even banal statements or questions driven by the calendar or the whim of a writer that may not have anything to do with the brand in question.