Traditional Media has been doing it for years, building an audience through programming and marketing and then turning around and selling your business the opportunity to talk to their audience.
Social Media is the opportunity for YOU, the local business owner to create your own audience to communicate to and through. Building an audience in social media truly isn't much different than what traditional media has done. Create entertaining content, and give the people what their looking for and they will come.
With social media you have the ability to create the programming and the messaging to build an audience on your social media outlets. Twitter/Facebook etc all have audiences looking for ways to be entertained, create the proper content and you'll have an audience that you then can engage with daily..
Just as TV, radio and print or any other kind of advertising is not the end all, or offer some kind of magic pill that heals all ills, this is just a layer of what you can and should be doing.