It's no secret that social media marketers focus a lot of energy on teens and young adults, traditionally the largest demographic on social networks. However, a new eMarketer study reveals nearly 28 million moms will be using social networks by the end of the year, representing approximately 82 percent of Internet-using matriarchs with kids under 18. These moms seem to be especially fond of Facebook and the female-friendly Pinterest. They're also more likely to use social media than the general population by an 80 percent to 55 percent margin. Fortunately for marketers, moms are also among the social media users most likely to base purchasing decisions on peer recommendations, according to a recent Performics report.