Celebrities behaving badly. The public fascination with the genre goes way back, to a time when such questionable deportment was, well, good. Good in that it seemed to the hoi polloi romantic, adventurous or otherwise intriguing, the kind of conduct in which you might dabble yourself, if only you dared. Or, truth be told, if the opportunity presented itself, which of course it wouldn’t, such being the divide of opportunity: for the high-flying famous, glamorous debauchery; for the merely mortal (read, us) plain bad judgment.

Once upon a time, celebrity scandal pulsed with sophistication. Edward VIII scorned his throne for a twice-divorced conniver. Elizabeth Taylor ran through husbands like Smart Water, her Cartier cache and box-office clout staying rock solid even as her femme fatale ways devastated poor Debbie Reynolds. Brahmin-voiced JFK bedded not a chubby intern, but the sexiest bombshell in the world.

Ingrid Bergman left home, hearth, husband and daughter when she conceived, by a Mediterranean movie director, out of wedlock. Engrossingly sinful trailblazers all. Even when the bad behavior ended in tragedy — from Stanford White to Sid and Nancy — however tawdry the reality, the public take was of mythic romance. Running off with a rock star, more husbands than shoes — such decadence belonged to the entitled elite. But we could dream.

Whatever happened to aspirational bad behavior? It died, a victim of various circumstances. With celebrities now covered so relentlessly, from Starbucks in the morning to the after party in the wee hours, they suffer from diminished-mystique syndrome. At the same time, many care not a whit about cultivating mystique; it’s often preferable to act “normal.” Today, spies live in Yonkers, while TV stars shop Whole Foods. And in a permissive society, what once shocked is now a lifestyle choice. Bastard babies? Dime a dozen. Rehab? Who hasn’t? Nip/tuck? Just don’t overdo it à la Heidi Montag, who followed 101 procedures to her pretty, 23-year-old self with nearly as many press accounts bemoaning how sad it all made her mother. And let’s not forget celebrity-gets-fat fodder. The public loves it, but talk about lowbrow.

Today’s bad celebrity behavior is just plain bad. Tacky bad. Enough so that, even as we lap it up, we feel not awe but superiority. The past week or so has offered a triptych of such opportunities. First up: The latest on Lindsay Lohan, who has shelved monster talent in order to spend her entire young adulthood to date going out. Not to exotic places, but to venues populated by run-of-the-mill cool types, famous and not. She’s gone out, out, out. Now she’s going in, to the slammer.

Next: the Us Magazine cover story on Bristol Palin and her on-again fiancé, that hunk-’o’-burnin’ idiocy, Levi Johnston. Girls run off with bad boys all the time, always have and always will. But in the past, when deemed press-worthy, he was likely a notorious roué or dangerous musician, not a dropout trying to muster enough gumption for a GED. This is a girl famous for exactly two reasons: having a wacky mom and getting knocked up (the current previously noted ubiquity of out-of-wedlock children not-withstanding). So far, Bristol has made the best of her circumstance: her own condo; a job in a doctor’s office; drives the baby (the gorgeous baby; turns out, Levi wasn’t a total bust) to the sitter. Only now, Bristol’s back with loser Levi. You want to say, “No, Bristol, honey, no. Listen to your mom; she’s right on this one. Better a single mom supporting yourself and a baby than a put-upon wife supporting yourself, three babies and a ne’er-do-well cheating lout of a husband.” And make no mistake, he will cheat. Up there in the cold, in between moose-hunting trips.

Speaking of louts: Mel Gibson. No, wait. Unfair to Levi Johnston; there’s no comparison. Is there a breathing entity on this earth more disgusting than Gibson? And not only disgusting. He’s also stupendously stupid, because anyone listening to his tirades could tell by his former girlfriend Oksana Grigorieva’s calm demeanor that she knew the tape record was on. Has he never seen an episode of “Law & Order”?

Elizabeth Taylor and Richard Burton were said to be a lusty pair. We’ll never know if, in a moment of rage or one more amorous, he ever suggested that she “just [bleeping] smile and b--w me, because I deserve it!” If yes, delivered in Burton’s glorious Shakespearean Welsh cadence, the sorry script no doubt sounded more refined.