Studies show that people who are paid to do something are more inclined to quit when payments cease than people who were never given any financial incentives — and that could have serious implications for brands that lure Facebook fans with offers of discounts and freebies, writes Mya Frazier. Cash and other incentives distort the social-media ecosystem and impede genuine engagement, Frazier argues. “Can sharing for sharing’s sake survive in an ecosystem that increasingly turns every sharing exchange into monetary reward?,” she writes. PBS