Links from social networks like Facebook, Twitter and Google+ are gaining popularity as they are becoming very effective in SEO now. And the fact that links from Google+ affects more cause it is owned by google.
Social Media and SEO together can cause very positive ripples in terms of creating brand awareness and content proliferation. The idea to use them in tandem should however not be restricted to increasing visibility. Promoting content via social links can really be an ingenious way to keep within the White Hat and Penguin markers and yet have a superb impact.
Why didn't you mention Linkedin? I have heard that many people there promote their business and make targeted ads and attract subscribers, but I do not know how to do this
Links from Linkedin are really gaining popularity and this social network is good for promotion in SEO. But you need to understand that without a good number of LinkedIN followers , you will not leave only for SEO. When there are a lot of subscribers it is easier to start