A friend of mine, an ad guy and utter sartorial snob—custom-made suits, cashmere sweaters—fancies himself an unmovable rock of personal style. He was wearing his shirttails hanging down the front of his pants long before this look got tagged as a trend, and my friend swore, with conviction usually reserved for damning unfaithful girlfriends, that he would never, ever tuck in his shirt. Turns out he was just going through a phase, much like a teenager who has a brief but passionate affair with Dep. His shirttails are now firmly back where they belong—inside his trousers—every day.

Unfortunately, the majority of untuckers—the guys still blindly clinging to the ďrumpled suit, visible tails, and All StarsĒ formula fomented by Ryan Adams, Julian Casablancas, and their ilk at the beginning of the decade—have yet to admit to themselves that theyíre wrong, that the bell has long since tolled for the Iím-dressed-up-but-not-really look.

ďIt was cool and unstudied when those guys first did it,Ē says Michael Bastian, the former menís-fashion director at Bergdorf Goodman who just debuted a namesake line of tailored menswear. ďThe problem with the ones doing it now is you can see theyíve thought about it.Ē

Indeed, shirttails that blow in the breeze betray one of two mind-sets—both of which reflect poorly on the wearer. One is that you think flouting traditional fashion mores makes you appear coolly rebellious. I may be wearing this bespoke shirt, but no one can make me stuff it in my pants. On the contrary, liberated shirttails paired with a tailored suit look hopelessly jejune. On a 12-year-old Catholic-school kid, such a blatant sartorial middle finger might be endearing. On a 30-year-old itís pathetic. If thatís the best way for you to demonstrate that no one can tell you what to do, perhaps you should shift your attention from your wardrobe to your career.

A subset of untuckers wears a sweater over the emancipated shirt, allowing the fabric to hang down past the hem of the pullover like a loincloth. Perhaps Jeremy Piven, Jimmy Fallon, and others who favor this arrangement consider it boyishly unkempt. It isnít; itís sloppy and contrived.

The other, equally misguided motive for treating a button-down shirt like a baby-doll dress: It conveys nonchalance, a casual indifference to those tired old rules of dressing—like tying your shoes and zipping your fly. You roll L.A.-style. Sure, you look relaxed. A little too relaxed. A collared shirt billowing over jeans isnít merely cheesy but vaguely vulgar—like you just came from a quickie with a table-waiting actress wannabe. And maybe thatís what this breed of shirt manipulator—Josh Duhamel and Carson Daly among them—is trying to convey. Alas, rather than attracting ladies, the untuckers are more likely frightening them.