What is the purpose of social bookmarking, does it really work and how can we make it work.

A brief introduction: social bookmarking sites like delicious and digg exist to allow people to keep their bookmarks all in one place so that they can be accessed anywhere from any computer. The idea arose from the need to resolve one simple problem: our browsers can only accomodate a limited number of bookmarks. And even then it is difficult to organize and search for the bookmark you are looking for.