Week 8 Social Bookmarking

I have set up and tagged a few sites. My local library, our learning 2.0 and footy tips sites. It will be handy going to the one place to access all of these sites whilst I'm away. Will just have to remember login details for delicious. Not sure about "social bookmarking" why do I want to share these bookmarks? I noticed that my local library has been bookmarked by others.