social Bookmarking is one from long list of getting and generate traffic for your site, But you need to know how use it to build your followers.
you cant depend only social bookmarking for getting rank to your site but yes high page rank in social bookmarking will give you some help.
building your back-links need a lot of work on forums,AD,SB,WS and blog comments
its a big circle but they are related to each other some how.
so using only one factor (social bookmarking i mean ) will process your rank for 10%