Oprah Winfrey has struggled to keep viewers since moving to OWN: Oprah Winfrey Network, but she's still the first choice when the top celebs want to open up about the tough truths that can threaten to kill a career. She described her Jan. 17 interview with Lance Armstrong -- spoiler: He confesses to doping! -- as the "biggest" of her career. That's saying something. Here, a look back at the most recent Oprah-facilitated confessions: