"In principle, for certain groups of kids, it can work," said Judy Kuriansky, a Columbia University sex therapist. "Psychologically, when you make a public statement, you are held more accountable. You have to face the music."
A June RAND Corp. study showed that virginity pledges may help some young people postpone the start of sexual activity. Still, there is conflicting evidence. Last year, a Marie Claire magazine survey showed that 90 percent of girls who pledge abstinence don't keep that promise.
"Britney Spears claimed that she was a virgin publicly, and then her mom said she was having sex when she was 14," said Kuriansky. "For anyone it's difficult."
"Everything is multiplied by saying something, wearing something, doing or signing something," she said. "But if it's foisted upon kids who are not psychologically prepared for what it means or if they are forced into a ritual they don't understand, then there can be negative outcomes."
Black, now a photographer living with her husband of little more than a year in Texas, insists she made the decision herself. She refused to date throughout high school and savored her first kiss on the altar.
"I see my choices as very liberating. I'm not bound by disappointment or the broken heart of past lovers," she said.
To those who wonder how good sex could be without previous experience, Black's sister Khrystian Wilson, who is now engaged and has also never been kissed, said, "I stood next to her at the wedding and it was electric."
The largest movement to spread the chastity is called True Love Waits, started by Richard Ross, now a professor of student ministry at Southern Baptist Theological Seminary in Fort Worth, Texas. He led a Tennessee youth group in the 1990s, just as the national rates of teen sexual activity were peaking.
Since then, those rates have dropped, which Ross calls, "an interesting correlation." But he argues that in secular settings, where there is no religious imperative and little parental and community support, many teens pledges fail.
"These programs are more limited in their ability to shape student decisions," Ross told ABCNews.com. "The massive difference is making the promise in a faith community, surrounded by the entire youth group."
Today, at his former youth ministry at Tulip Baptist Church in Old Hickory, students begin discussion of "the promise" in Sunday school and at weekend retreats in January. Just before Valentine's Day, those who pledge to virginity attend a special ceremony with their parents, who give their teen a special "promise ring."
"It helps them believe that this is a big deal and it matters to my church, my family and all my friends in the youth group," said Ross. "It's a concept, an idea, a promise to God. We acknowledge it's tough, but we also say one wonderful thing about being a human being you get to choose."
Alec Cort, who now serves as a student minister, said about 75 percent of the youth group takes "the promise." "It's not a cure-all," he told ABCNews.com. "But for the most part it instills values of God, and its utmost importance takes root."
Nathan David House, one of his students, pledged in seventh grade, on the heels of two older sisters.