Bonnie Beck didn't always go by Bonnie D. Stroir (pronounced "Destroyer"). But the 29-year-old took on the name when she began playing roller derby in her early 20s. Roller derby has changed since it first became popular in the 1970s. Today, most leagues no longer allow fighting. But the basic idea is the same. Teams earn points when a player successfully navigates a path through the pack of skaters.