clipped from: www.pandia.com   
Social bookmarking sites are in many ways the ultimate folksonomies,

Social bookmarking sites are in many ways the ultimate folksonomies, categorising web content by an open process of tagging. The result is a road map of the web, based on the recommendations of people who have traveled it extensively.

every web surfer is a potential editor, licensed to categorize and recommend all kinds of web sites.
A decent amount of users is necessary.
The service has to have quite extensive documentation
  • More advanced users will want good import and export possibilities. Import is necessary for bringing old bookmarks from your browser or from another online bookmarking service, export is important for backup copies and to ensure that your bookmarks can go with you to another service if you decide to switch.
  • A good bookmarking service should have feeds (RSS and/or Atom) of tags or groups of tags.
    • have a blog so I can be kept up to date about new features, bugs, bug fixes and more.