“Social bookmarking is a method for Internet users to store, organize, search, and manage bookmarks of web pages on the Internet with the help of metadata.
In a social bookmarking system, users save links to web pages that they want to remember and/or share. These bookmarks are usually public, and can be saved privately, shared only with specified people or groups, shared only inside certain networks, or another combination of public and private domains. The allowed people can usually view these bookmarks chronologically, by category or tags, or via a search engine.” <wiki>
Social bookmarking is essentially a non-zero sum transaction (the interacting parties’ aggregate gains is more than zero). Everybody wins. Bookmark something for me today, and I will bookmark something for you tomorrow. This is the basis for reciprocal altruism. No strings attached. Rheingold explains.