Underneath the hubbub of election and market fever in 2008, another change was taking place: Americans were becoming increasingly aware of the global problem of sexual slavery. Mam is the most compelling face of that issue. As a girl, she was sold into prostitution in Cambodia. She doesn't know her age, her given name or any family members. But she knows how to fight human-trafficking, which in the past 12 months has claimed as many as 4 million girls and women.