Half of US online adults are Joiners, people who interact with social networks at least once a month. Very few are decreasing the amount of time they spend on these networks. More than three-quarters of Joiners visit Facebook regularly, but LinkedIn members are the most affluent. Social networks are an ideal way to spark word of mouth, since Joiners are more likely to spread product opinions and counsel friends and family before they make a purchase. While Facebook dominates this space, MySpace is still effective for entertainment brands, and LinkedIn can help you reach high-income professionals. Interactive marketers should check out and connect with existing fan pages and groups before launching their own.