A hundred years ago, we did our business face to face. Someone came along and invented the telephone, and I imagine there were a bunch of people out there offering courses and speeches about how selling over the phone was the next big thing. You can almost hear the business owners: "Pshaw! Talk on the phone? That's madness! We do business face to face."
If you think of your main website as your home base (be that a blog or a shopping site or a corporate site) and if you think of all the social networks as outposts, then you're halfway to understanding one of the best ways to market online, in my not-so-humble estimation. The trick is this: knowing when to engage on the outpost and knowing when to drive people back to the home base.
Before I was a blogger, I was an employee. After I became a blogger, I was someone with an opinion. I was a writer. I was a publisher. I was a business. In a word, learning how to use my voice set me free in ways that continue to expand and provide opportunity for me every day.