(CNN) -- Every post you "like." Every friend you add or fan page you join. Every place you check in, and every Web page you recommend. To you, those are ways to enjoy, expand and improve your experience on Facebook. To Facebook, they're the building blocks of a multibillion-dollar company. In business, there's a well-worn line that could apply to the social-networking behemoth: If you're not paying for it, you're not the customer. You're the product.
