Illustration: Emily Flake

If you bring up the subject of PDA, the same phrase always seems to surface: crossing the line. But isn’t crossing the line the very thing that makes it enticing?

Not according to Chris, 28, who regularly shows the girls he’s dating—and anyone in a ten-mile radius—how he feels: “Nobody gives a shit about what other people think here,” he says. “And every guy needs to mark his woman—they PDA to mark their territory.”

Gee, I’d always thought that people groped in public because they were so overwhelmed by raw, unmitigated desire and passion that they couldn’t contain themselves. Apparently it’s a lot like how dogs piss on trees.

Nicholas, 18, is clearly more romantic, or at least hormone-ridden: “People do it because they’re caught up in the moment,” he says.

“I am so happy with my boyfriend and I want the world to know it,” says Hayley, 23. “This doesn’t mean I am more affectionate with him in public than in private, but I don’t ever restrain myself from a spontaneous hug or kiss. I do, however, stay within the bounds of public decency—there’s no errant bodily fluid or grabbing anywhere that a swimsuit would cover.”

Ah yes, the swimsuit/bodily fluid line—a fairly basic one.

For others like Michael, 35, it’s the “Could I be watching this on pay-per-view?” test. “If you see it and the words sweet or tender or even awwww come to mind, then it’s fine. Otherwise, it’s porn.”

“That’s why only hot people should be allowed to PDA,” says a friend of mine who shall remain nameless. “Honestly, I’ve been with some women who I just didn’t think were that pretty, and that made me subconsciously reluctant to show the world that I was banging them.”

“But,” he continues, “I think if you really like someone, and are really attracted to them, you tend to touch them—even in public—without really thinking about it.”

Some people do it just to humiliate the one they’re with. “I love little PDAs because they totally embarrass the girl I’m with,” says Jason, 31. “I’ve stopped in the middle of the street, just to dip her and lay on a big movie-star kiss. Seeing her face get all red, but knowing she secretly loves it, is the best.”

That kind of affection makes everyone want to go home and make out with their partner, right? The problem is that some people don’t save anything for the bedroom. “When I see a massive amount of tongue and spit inches away from my face on the subway, I get a tad annoyed,” says 19-year-old student Melissa. “It’s often really young couples who seem, like, minutes away from a teen-pregnancy scare.”

So, what’s the protocol? “A good rule of thumb is that if you wouldn’t do it in front of your parents at age 13, then you shouldn’t be doing it in public at any age,” says Amanda, 27.

Me, I’m prone to agree with Hayley; it’s all fun and games until someone starts to lose fluids.

E-mail her at julia@timeoutny.com.

See previous Julia Alison on dating