EVEN AS CHILDREN, twins Cameron and Tyler Winklevoss stood out in a crowd. "People would always walk up to us and ask the same three questions," says Cameron. "Are you identical? Who's older? And do you get asked that all the time?"

(The answers: Yes; their parents have never revealed; and yes.) More recently, their 6-foot-5, 220-pound frames made them prime targets to be stopped and asked if they were the twins in David Fincher's The Social Network, which dramatized their real-life battle with Facebook...