Social Networking is a great tool to connect people with your business and it is easy to use. When starting with social networking keep in mind it is much easier to add then to take away so start slow. Maybe start with a blog, then add twitter. After that consider a facebook group and a linkedin group. After that you may be able to add specialized blogs and/or twitter feeds.
Before getting caught up on driving traffic your direction and being fixated on page rankings focus on bringing value to your customers and potential customers. Remember that climbing high in search results is about providing information that people care about. You can have six different blogs trying to astroturf your way to the top but at the end of the day if you do not provide value, i.e. you do not provide information people care about then no one will link to your information thus resulting in lower search rankings.
Starting out too fast will create a burden of providing consistent content to many different sources, sources you do not want to go stale.
Bottom line, focus on providing value first through social networking and start about slow.