McDonald’s compiled a 515-page dossier on one of its loyalty-program customers — using years of fast-food purchases to predict how often he would return, how much he would spend and even what he was likely to order. Reece Rogers, a journalist for Condé Nast-owned Wired magazine, discovered the extensive digital profile after requesting the personal data McDonald’s had stored about him. The file revealed a “Minority Report”-style trove of predictions about his future behavior, including that he would visit McDonald’s 2.16 times over the next six weeks and spend an average of $13.49 per order. The fast-food giant calculated Rogers...