Social bookmarking is a way for web users to explore, store, organize and deal with the bookmarks of sites and webpages on the web with the aid of metadata. Users save links of the pages that they would like to remember and/or share. These bookmarks are commonly public, and could be kept privately and shared only with specific people or groups or can be shared only inside certain networks and domains.
Why do I need it?
For bloggers and webmasters, social bookmarking is a useful way to access a combined set of bookmarks
from various websites, organize packs of bookmarks, and share bookmarks with groups and contacts. People have found social bookmarking to be useful as an comfortable way to provide numbers of informative links to the bookmark users.
What are the disadvantages?
It's popular, so some exploiters have started counting it as a tool to use along with SEO to make their websites more seeable. The more frequently a webpage is submitted and tagged, the better is the chance it has to be found. So, spammers have started bookmarking the same webpage multiple times and/or tagging each page of their website using numerous popular tags, to make their website more Search Engine Optimised, yielding the developers to constantly adapt their security measures to defeat the abuses.
If you are social then I will tell you how to add Social Bookmarking icons to your blog. So to get updates subscribe to Simple Blogger Tutorials.