If you say you haven't, you're a prude. If you say you have, you're a slut. It's a trap. So spoke Ally Sheedy's character in "The Breakfast Club" on a topic that inspires continued fascination: virginity, the v-card every woman is supposed to hold onto at the time in her life when she is often obsessed with turning it in. Virginity is a tricky concept. As a culture we've explored it in our films , TV shows , books and classrooms , but we still don't have a clear-cut definition of what it entails or why it's important.