Social bookmarking sites capitalize on the principle of the wisdom of crowds when deciding what content to promote to the sites’€™ front-pages. What happens as these sites start to mature is that a group of prolific community members rise above the rest of the community. Once a select group begins to be considered ‘€˜better’€™ than the rest, sites relying on socially driven content run into the information cascade problem and the wisdom of crowds doesn’€™t work anymore.
The Japanese discussion board 2ch.net may have the answer.