Albeit social bookmarking is for storing your favorite sites, blogs, article and social media you can benefit your seo exercise through it. The bookmarking websites are not just hanging place anymore. The sites offer a search capability that makes you website or content accessible to reader. They can be found by another user. You can make your link private if you do not wish others to access them. but keeping it public is a good choice if you wish to proliferate your content on web.
The most important gain is that your word spreads and your article is indexed faster by search engine. If you look at your browser you will find a bookmarking tab use it and you will know quickly what it is. This tab helps you to bookmark your favorite websites and blogs hence you do not have to search them every time.
The professional bookmarking sites offer much greater features and when you submit the link to them use tags that describe your content. There is an option to place the link is a related category do it. This way all your related links will be marked topic wise. This will increase the search potential of your links and hence the exposure. Backlink benefit is less through these sites as they are no follow but nevertheless do not ignore these sites in Internet marketing campaigns.
Another benefit you get is connectivity with like minded people who begin to read your bookmarked content. They enroll as you friend or fan and have access to your bookmarks. Thus you get a constant readership of your content articles and blog entries.