I have a good friend whose Facebook friend list is only 30-people long. How does she fend off the countless inquiries from old junior high lab partners and former suitors? One simple rule: If she would invite you to her house for dinner, she’ll be your friend on Facebook. Sure, her standards are tougher than most, but for consumers from the coveted age and income bracket, true brand engagement via social media requires more than showing up on a page. Companies have to be worthy of connecting offline, so that the virtual relationship is an extension of the real one we can touch and feel. Worthy dinner companions, if you will.

When General Motors pulled its $10 million ad account from Facebook just days before the social site’s IPO, it created quite the unintentional buzz. GM downplayed the remark and made it clear that it would continue to engage customers via Facebook, but the decision surely had plenty of corporate marketing people second-guessing their own paid social media efforts. GM said its decision came down to lack of proof that the paid ads work. Ford smartly jumped on the opportunity to posit another reason, also echoed in this Forbes.com analysis.

So, how does a company cross the threshold from utilitarian product or service provider to a partner worthy of a social invitation? It’s all about valuable content. Let’s take a look at Nike+. Somewhere along the way, a masterful marketer (or perhaps intuitive engineer/avid runner) launched a symbiotic relationship that allows people to track fitness goals and share their performance with the world on Facebook.

Now, let’s go way back to 1904, when Jell-O first began distributing its recipe book door-to-door for free, driving up sales significantly in a short timeframe. Using the same content-driven marketing approach today, the company has cultivated a virtual cooking circle on Facebook.

So, what is the magic formula for successful sales via social channels? Have you had success building a following motivated to action? Share your challenges, successes, and lessons learned in the comments.