Performance-apparel retailer SmartWool built a loyal and engaged Facebook following by holding campaigns encouraging fans to share stories. The company posts photos of fans celebrating accomplishments such as finishing a first marathon and holds lighthearted campaigns such as "Strip to Your SmartWool," which asked users to submit images of themselves wearing nothing but the company's products. As a result, the company has a referral rate of 96%, said SmartWool's Molly Cuffe.