The New Yorker has an excellent article by Margaret Talbot on "Red Sex, Blue Sex." She starts with the puzzling fact that evangelical teenagers talk the best game about saving sex for marriage, but actually have premarital sex and premarital babies at higher rates than kids in other groups do.
Part of this problem is that many people talk the talk of evangelicalism in general, but don't walk the walk. Evangelical teens who are the most religious and the most embedded in strong church families and strong religious communities really do have lower teen sex rates.
In many communities, though, especially in the small-town South, born-again talk is just conventional. Kids with conventional premarital sex lives -- that is, they have some premarital sex -- will also talk the conventional anti-premarital sex talk, especially to grownups. This doesn't prove that evangelicals are especially hypocritical, but rather that most people are conventional. It is like people in "tolerant" communities actually being very intolerant of people unlike them (such as evangelicals). Most people are conventional. Most communities have some conventions that conflict with one another. Therefore there will necessarily be a group of inadvertent hypocrites who follow one convention at one point, and another convention at another.
The "blue sex" group is also interesting. Blue states have lower teen pregnancy and divorce rates than red states. The key seems to be the later average age of marriage in blue states. This reflects the fact that people in blue states have, on average, more education, which delays marriage. Later marriage doesn't delay sex much, but it does delay marriage. And some people who delay marriage arrange whatever sex they have to produce fewer non-marital babies - enough to significantly improve statewide averages. The risk of later marriage, though, is infertility or, worse, unhappy never-married life.
The most interesting group to me were the kids who did successfully avoid teen pregnancy and too-early marriage, without utterly avoiding or condemning sex. Mark Regnerus, the sociologist whose work on religion and teen life is the heart of Talbot's article, found that the most successful middle way was practiced by teenagers who had big plans for their lives that they actually followed. Those who had high ambitious and had mastered the basic bourgeois skill of deferring gratification were the most likely to avoid teen pregnancy -- and avoid addictions and reckless accidents. They lived carefully because they had bigger things they wanted to do with their lives.
Going beyond what Talbot and Regnerus show, I think I see in these plan-ahead kids a more proportionate sense of the importance of sex. Some kinds of religious conservatives treat sex as bad. This position is not nearly as common as it used to be -- it seems to exist more in liberal fears about "fire and brimstone" preaching than in the actual sexual attitudes of evangelical Christians. More common, though, is to find religious arguments for marital sex as a unique and transcendentally wonderful form of intimacy. You should save sex for your spouse because no one else deserves something so wonderful. This seems to me to elevate sex beyond what it can really deliver. On the liberal side, there are still some sensualists who treat sexual passion as the door to Deep Truth, but they are about as common as fire-and-brimstone preachers. More common are liberals, secular and otherwise, who treat sex as a fun game - so why not play it with whoever is good at it? This, too, seems to me an erroneous estimation, too shallow rather than too deep.
The middle sex view is neither too transcendent nor too flippant. The middle group that Regnerus points to see sex as a good thing that is best done in marriage, but is not bad in relationships that might lead to marriage.