Regarding the issue of whether adult sexual activity can cause harm to third persons, this story makes me feel morally obligated to issue a qualification. Or maybe that would be a caveat. Anyway, if these facts are correct, I'll have to issue something:

MOSCOW, Idaho (AP) - A 22-year-old carnival worker blames two friends having sexual intercourse in the back seat of his car for an accident in which his Chevrolet S-10 Blazer struck a telephone pole.

Joshua D. Frank, who is living in a trailer parked on the Latah County Fairgrounds, pleaded guilty Monday to a misdemeanor charge of failing to notify a police officer of a traffic accident. That's after he left the vehicle at the site of the mishap. He was fined $188.

Frank told Moscow Police Department officers that he was driving the vehicle near downtown early Saturday while a man and woman were having sex in the rear of the vehicle.

According to a probable cause affidavit, Frank told authorities that the actions of the pair in the back caused the Blazer, which "was top heavy anyway," to become "tippy" and lose control.

Frank left the accident scene with a minor head wound and returned to his trailer.

The other two occupants of the vehicle were treated for injuries, according to the affidavit, though further information on their condition wasn't available.

there is no legitimate moral argument that what one adult does sexually with another consenting adult does intrinsic harm to anyone else, much less society.

There's an old saying "as long as you don't do it in the streets and frighten the horses" which comes to mind here. How far that goes, I don't know. (There are people who are more afraid of sex than horses are, and some have called them "erotophobes," so it isn't something to be dismissed airily.) My argument presupposes that sex is done in private, and whether the back of a Blazer is a private or public place, I'm not sure. But is privacy really the issue here? No one complained that these people were visible; only that they made the Blazer "tippy." Something like that could have occurred if the vehicle were curtained or paneled.

So, perhaps the rule should be that sexual activity should be performed not only in private places, but also in places where the moving and the shaking which tends to occur is unlikely to cause injury or property damage.

Obviously, sex should not be engaged in while driving or operating heavy machinery. Anyone who thinks I am engaged in frivolity here should bear in mind that this is a very serious issue, and at least one film has been made which grapples with the issue of "auto"-eroticism:

....an entire cult formed around the erotics of car crashes, including Colin Seagrave (Peter MacNeill), a former race-car driver who collaborates with Vaughan in restaging famous car crashes (such as those involving James Dean and Jayne Mansfield), and Gabrielle (Rosanna Arquette), who wears leg braces and a full-body support suit like fetishistic paraphernalia. It all sounds like a joke, but the film rigorously, solemnly follows these characters as they compulsively replay and comment on a crash video in Swedish, restage accidents, have sex in cars, photograph people having sex in cars and crash victims (one of Vaughan's activities), or crash their cars into one another's as a kinky kind of love play.

It's probably a good idea to avoid sex in canoes too, as they're inherently unsteady. See how complicated this can get?

And what about earthquakes and other acts of God? I've been through several of them, and I'm glad I wasn't having sex, because it might have been very difficult to run for cover. I was in the 1989 San Francisco earthquake, and I got stuck on the Bay Bridge (which actually broke). Clearly, sex would have been a bad idea at the time. If your city is experiencing a hurricane or tsunami or something similar, that's probably also a bad time to be screwing. (I mean, what if the dam breaks right in the middle of, you know....) Ditto for wars, urban insurrections, nuclear attacks, etc.

There's probably stuff I'm missing, but you know, I really hate writing about sex, because it can be disruptive. (BTW, I would never blog while having sex or have sex while writing a blog post, so I'd advise against that too.)

It probably comes down to common sense.

(Geez, I almost said "There is no hard and fast rule.")