Godes cited Lee Jeans as one company that generated terrific word of mouth for its brand. A few years ago the company connected with players on online video forums to drive store traffic from teenage boys. To gain access to a special game, players had to get a code from the labels of certain Lee products.

Teens didn't have to buy the jeans, but they did have to go into a retail store to find out the code. Players in gaming forums shared the tip about the jeans and the game, and the clothing company was pleased with the results.

Lee definitely took the right route. According to a study released by MTV and Nickelodeon last summer, most teens trust their friends' opinions more than those of marketers. A whopping 88% of the 18,000 16- to 24-year-olds surveyed said most of their Web-site visits are prompted by links sent from friends.