"There's an erotic undercurrent about being in control of a situation," says Edward Ratush, a psychiatrist and sex therapist in New York. "It's a very ego-focused thing for the guy."

Albert (his middle name), a good-looking 29-year-old who's fairly well-known in the music industry, says he asks the women he dates to have anal sex with him because it raises the level of intimacy in the relationship. He doesn't demand anal sex—especially not if it's a one-time hookup—but he won't commit to a woman who refuses to grant him a backstage pass. "I had a girlfriend who I was with for a long time and she wasn't into it," Albert says. "There was definitely a thing in the back of my head like, 'I can't marry her.' How can I, knowing I can't go to all the places I can go with her? The physicality of it, being painful or whatever, shows how comfortable the girl is with you." Here, he pointedly stops short of romanticizing screwing a woman rectally. "Ideally, every girl is a disgusting pig who wants it," he says. "But only with you."

There's evidence that some women do like anal sex, and that they're as into having it as some men. The dating website Lavalife recently polled 20,083 members in its "Intimates" section. Thirty-five percent of female respondents claimed to enjoy anal sex. "It's a myth that every straight man wants it and the women who give it up do just that," says Tristan Taormino, author of The Ultimate Guide to Anal Sex for Women.

Dawn (her middle name), a 34-year-old married woman who lives in Ohio, first tried anal sex at her husband's suggestion, only to discover that she was much more into it than he was. "It's better," she says. She'd like to have it more often, but it's currently off the table. "He's got more hang-ups about it than I do," Dawn says.

After the forbidden territory has been conquered, some men find they have psychological issues with the act. Even Albert, the one who won't tie the knot without a key to the back door, admits that. "You're thinking, 'I don't want to hurt her, and I don't want shit to squirt out at me,'" he says.

So if you can't be certain whether the woman's enjoying herself or just submitting to peer pressure, and the act itself can be unpleasant, what's the motivation for demanding it? For Todd, so his friend says, it was about maintaining emotional distance. Albert says it's about enhancing the intimacy between two people. But the more plausible explanation is that it's about accessibility—and instant gratification. Now that anal sex has been propelled higher on the mainstream menu by a hypersexualized culture and the proliferation of porn (see Ass-Hole O Mio and the Anal Excursions series), some men can't help but order it. And some women feel the need to offer it.