In the days before social networks existed, people in chat rooms would often ask each other "a/s/l?" to find out who they were talking to. Today, social networks ask users to provide information on everything from hobbies to favorite sports teams to memorable quotes so other members can see who they're connecting with.

A similar evolution is taking place in marketing. For years companies targeted potential customers based on such demographic basics as age, gender, and zip code. That information is still immensely valuable, but is no longer enough. To keep pace with the growing emphasis consumers place on the relevance of companies' communication with them at every touchpoint, savvy companies increasingly are looking deeper into customers' personas—and then using micro-segmentation, behavioral or transactional targeting, and online data gathering to develop a more comprehensive understanding of who their customers are and how to better serve them.

"The purpose of marketing is to harvest cash flows by changing customer behavior," says Don Peppers, cofounder of Peppers & Rogers Group. "To do that you have to motivate them to do something, and understanding how to [do so] involves knowing what your customers' needs are, in a deeply human sense."