Social bookmarkig is sites that let you add a list of your favorite sites. You can join groups so others can look over your list and sites. Most sites do not get good traffic. They get traffic but lookers no buyers. The most popular sites on social bookmark sites seem to be humor and celebrity related.
Social bookmarking sites allow deeplinking, are free and besides they are social. you can have a profile, talk to your friends, send them your favs, receive their favs etc etc
Social Bookmarking sites are human edited Search Engines.People add content to then and vote for making them best. They are very good for backlinks and traffic.
Social bookmarking Is a way for internet users to store, classify, share and search Internet bookmarks. Ranking a Web site by users who like the content rather than by the total number of links to the site. Social bookmarking sites such as del.icio.us (http://del.icio.us) let users tag their favorite sites with key words and post them for others to see.