There are several reasons I find these pledges ridiculous:
1.
They don't really work. There is
some delay in starting intercourse, but not much--and some of that delay can be explained by other factors. The vast majority of kids who take the pledges are still going to have premarital sex. While the STI transmission rates are the same, it seems that the pledgers' diagnoses are made at much later stages--which sets the stage for major problems later on, including cervical cancer and infertility.
There's also the studies out there that suggest that once pledgers are sexually active, they're less responsible. Since that could be a side effect of abstinence-only education, I won't put that solely on the pledges.
http://www.nytimes.com/2004/03/10/us...rely-kept.html
http://www.usatoday.com/news/health/...-pledges_N.htm
2.
It's a way to control female sexuality. Your father controls your sexuality until he passes it off to your husband. The imagery of locks and keys is a little gross to me as well. I understand parents not wanting their kids to be hurt but this takes it to a whole other level. Like a reverse Electra complex.
Furthermore, it increases the Madonna/whore duality.
This sounds like an extreme case, but check this out:
http://www.glamour.com/sex-love-life...1/purity-balls
3.
It puts the responsibility on girls. While girls are exhorted to "stay pure," there's no corollary for the boys. While I'd imagine that there are plenty of young men who take these pledges, they're geared towards women. There are no mother/son balls--and any woman who organized such a thing would be pilloried.
4.
Kids are encouraged to make these pledges when they're too young. I'd imagine the guilt and irresponsibility once sex actually happens is related to this. While there are some fast kids out there, most 11 and 12 year olds aren't thinking about sex. They also have very black-and-white views of the world. It's very easy to get someone that young to make a pledge without really understanding what it means.
It also appears that some of the surveys supporting the pledges only focused on younger kids who had taken the pledges within the past year. I'm sure that made the numbers look better than if they had waited to see what happened 5 years out.
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Don't get me wrong--I'm not anti-virginity. I think that boys and girls should wait to have sex until they can handle the emotional and physical responsibilities and consequences.