Social network are website that provides registered members to share online resources like images, texts, voice and hence improving search engine ranking etc
The popular social networks are
- Facebook.com
- Twitter.com
- Linkedin.com
- Delicious.com
- YouTube.com
Visit this website for more insights about social network dominance http://searchenginewatch.com/article/2064680/Social-Media-Around-the-World-Current-Trends-and-Future-Growth