Social Media has been a hot marketing topic for some time but it has very little value! Don't sink more than five hours a week into this low-value advertising.
A study by Outbrain says that Social Media lags for Traffic Sources. The results of that report has a small delta to most sites we manage.
Search is far and away the leader (41%), second is content sites (think Digg, Reddit). Portal (AOL, MSN)and Social are third and fourth with a sum-metric of 28%.
Our opinion is that driving Social Media should be a third order priority. At this time simply posting new products, service announcements, company news & links to Social Media is sufficient. The traffic-source numbers are just not there. There are eye-balls yes; but they don't engage as much.
All this of course will change over time. Until Social Media has some real traction our advice is to cover the basics, get the branded accounts/pages and make some posts. Keep the primary focus on Search Optimization then Local (Places, Yelp).