Leaders of the abstinence movement firmly believe, however, that teaching kids about the mechanics of sex and contraception "arouses" them, sparking them to have sex. They claim that those who break their vows were not "strong" pledgers to begin with, and that many more teens do keep them (teens the researchers didn't speak to). "Kids who abstain are not out there breaking hearts; they're not dogs in heat. They go on to have great, intimate sex," says Leslee Unruh, president of the Abstinence Clearinghouse. "The purity movement celebrates sex but not sex outside of commitment."

Girls who are getting married do need information about sex, Unruh continues, and she's there to provide it. (On one occasion, "I had a girl call me from her wedding," she says.) "I let them know what to expect, that there might be some discomfort," and she gives detailed information about touching and lubricants when necessary. Unruh thinks purity balls are a commendable way to get girls who want to stay virgins to do so. As she says, "They help girls realize that their fathers care deeply about their future, and then they decide to keep themselves pure."

Many experts strongly disagree. "Virginity pledges set girls up for failure," contends Kindlon, who specializes in adolescent behavior. "I like the father-daughter bonding part of the balls, but it is unfortunate that it is around a pledge that is doomed. I always counsel parents to try to encourage teens to delay sex. But when you completely forbid teens to be sexual, it can do them more harm than good. It's like telling kids not to eat candy, and then they want it more."

"When you sign a pledge to your father to preserve your virginity, your sexuality is basically being taken away from you until you sign yet another contract, a marital one," worries Eve Ensler, the writer and activist. "It makes you feel like you're the least important person in the whole equation. It makes you feel invisible."

It's not hard to imagine the anxiety young women must feel about being a purity failure. Carol-Maureen, an acquaintance from my hometown of Fargo, North Dakota, who got a purity ring in seventh grade and still wears it at 22, told me, "If I had sex before marriage and my parents found out, I'd be mortified. I'd feel like I failed in this promise to them, even though it's really not their business."

Marie, a Texan I met through a colleague, took a virginity pledge at 14 but actually felt no shame about breaking her vow a year later. "When I took the pledge, I was true in my heart, but as I got older I had a broader world view," she says. Still, she snuck around to have sex with her boyfriend so her parents wouldn't find out, and ended up getting pregnant at 19; she married quickly thereafter. Would she ever ask her son to take a virginity pledge? "No," she says. "I don't want him to tell me something just because he thinks I want to hear it and then lie to me about it."

Figuring out your sexuality on your own terms is a major passage into adulthood. Back when I was 19 and contemplating having sex for the first time, I presented my virginity to my boyfriend as this great treasure he could take from me. He looked at me and said, "But I don't want to take anything. You should be having sex with me because you want to—and if you don't, then you aren't ready." I was embarrassed by the smack-down of my "gift," but his words made me realize sex wasn't just something to give to him but something to do for myself, too. Learning that was more meaningful to me than actually having sex.