While social media might stand on its own as another way to draw customers to your site, the use is similar in that social media should be used to draw people to your public-facing webpage. You do not want a Facebook page to be your main home page, even if your cousin's nephew makes awesome FB pages in between college classes. Yes, you want likes and a following, but if you post to Facebook or Tweet, it should not be done to keep Facebook or Twitter in business.
Passive Ninja can add like buttons and comment areas if you're looking for social media interaction. We can work with you on a plan to choose the best use of resources to maintain a social media presence and following that leads to customers coming to the site we design. Ten years from now, when current social media is as irrelevant as Myspace (remember that?), you will still have a website with ten years of content and growth documented for your customers. A real website is the only guaranty that your company history is documented and that you own it.