Measurement is always a key topic. Via Revtrax:
The Unique Power and Value of Social Promotions
Social Promotions have a special ability to drive trial and loyalty far beyond other types of digital coupons – by combining the activation power of a promotional or coupon offer with a seamless way to share an offer, and presented with a personal recommendation or referral. They leverage relationships and personal good will to spread brand and promotion awareness, to build brand equity, and to strengthen consumer commitment to the product and brand. Well-designed social promotions can also be an incredibly effective way to help initiate a new direct, long-term consumer-brand relationship via email capture. Sharing a promotion isn’t just additional distribution, it’s an offer delivered along with a personal stamp of approval. We see our clients deploying social promotions with extraordinary results for both mass- and niche-market products. For products with small niche markets, or for products that might carry some level of stigma, such as specialized personal care products, social promotions can be an incredibly cost-effective way to identify and reach new customers. ... "