Well, I can say, Social bookmarks as a dairy. In our dairy we can note about our meetings etc. But in social bookmarks we can save info about our favourite websites and we can assign some tags to them and can categorize and organize in a easy manner. That will help us to search sites very easily from our collections. That is the real use of bookmarks. As well as you can get more friends over there too. Apart from that, nowadays, most of the guys are using social bookmarks to promote their websites. Say, a site www. yourdomain.com was bookmarked by serveral guys/girls, So, search engine will give more priority to such sites..... There are serveral social bookmarks sites, You can check it other threads here or you can just goolge to get more info. As well as there are some autosubmissions tool too, Here is one of it, just enjoy these,
Social bookmarking service. Fast tagging and posting to all major social websites - SocialMarker.com