Social networking adoption is currently a two-tiered landscape: Fifty-seven percent of consumers use just one social network while 43 percent belong to more than one. We call these two groups “single networkers” and “multiple networkers,” respectively. Facebook, with its network-effect-driven scale, dominates. LinkedIn and Twitter follow at a distant second and third. The social networking world will continue to be defined by two tiers for the foreseeable future. This report, based on data from GigaOM Research’s 2012 consumer survey, examines the social media audience and the differences and similarities between the two tiers.