And this is what makes Google Plus a worthwhile contender, seeing as it is really an extension of Google Search. And then there's the opportunity to use YouTube off the back of G+ Too.
I only use Facebook seriously for a few local business directory websites I run because I know the audience spend a lot of time on Facebook, and reaching them with paid advertising is worthwhile due to the low competition. The key is too funnel your slice of Facebook into an email list or retention page of some kind.
Some of my clients put a lot of stock in Facebook to the neglect of their website. So I think it has its place but if I was starting out today and had a choice of Social media, generally speaking I would go for Google Plus, Youtube, Twitter and Facebook in that order. Although for the local biz directories I did start with Facebook first (Google Plus wasn't around back then)