For the last decade, Facebook has helped people separated by physical distance to reconnect and remain close. And it’s also been the place where those same people have found themselves alienated from one another because of both real and fake news. James Jacoby talks with us about whether or not Facebook is a net positive for society, the subject of his two-part Frontline investigation “The Facebook Dilemma,” which airs Oct. 29-30 on PBS stations.