Social networking has become important for marketers due to a weak economy, media fragmentation, and consumers expecting personalization. Social media refers to internet and mobile-based tools for sharing information through words, pictures, video and audio. Social networks outperform other categories in key metrics. They have evolved from one-way information delivery on Web 1.0 to two-way interactions on Web 2.0 and knowledge-based interactions on Web 3.0. The key social networking sites reviewed are LinkedIn, Facebook, and Twitter.