Good branding is about knowing your market. Not "knowing" as in "being acquainted with", but something much more intimate. Biblical, even. A successful brand identifies its customers, understands them, and finds out exactly which emotional buttons to push in order to wring maximum profit out of those potential purchasers.

That's how it's supposed to work, anyway. But sometimes, the market gets away from the marketers. Take Ralph Lauren. The company has spent nearly 50 years defining and refining preppiness. Its website is full of vomtastic talk of "American style" and "inviting people to take part in our dream"; the advertising is full of clean-cut boys starring in what could be a burlesque versions of The Great Gatsby. And then it turns out that some of the biggest fans of the label aren't gilded Wasp youths after all, but thick-set and stubbly Mexican drug dealers.

In 2010, the Polo brand got some possibly-unwelcome exposure when Edgar Valdez Villareal – linked to the Beltrán-Leyva drug cartel – was arrested and presented to the press in a green RL polo shirt. A few months later, José Jorge Balderas Garza (also suspected of drug trafficking) was arrested for a shooting while wearing the blue version. Alleged assassination attempts and drug dealing don't sound very much like Ralph Lauren's dream at all, actually.

But, like many fashion labels, Ralph Lauren's main asset isn't good stitching or nice silhouettes: it's "aspiration". The whole point of its absurdly precise leisurewear is to give the wearer a honeyed glow of social confidence. For the Mexican children who see narcos as role models, the Polo look becomes something to imitate, and knock-off versions are readily available and widely worn.

This is the sort of success a label would happily do without: sure, the brand is popular, but with people who've got no cachet to share, and worst of all, no compunction about shopping for fakes instead of the real thing – both cannibalising sales, and turning off those carefully nurtured core customers. It's a position that Burberry found itself in early last decade, when it became bound up in what was nastily termed "chav culture" and its distinctive plaid turned up all over Daniella Westbrook and on baseball caps on the heads of sport-casual types. A design that had been a discreet marker of luxury became a sign of something supposedly much less desirable, and ultimately that hurt the company's sales.

Pity Burberry's chief creative officer Christopher Bailey as he worked to disentangle his brand from its market-stall mimics without coming off as a raging snob. It's not exclusive to sell trench coats for around a grand or two a pop, he explained in a Guardian interview, it's (here it comes again) aspirational: "that word exclusive – it suddenly says, 'you're not good enough for us'," he said.

Brands, of course, need to make their customers feel loved and cherished, but deep down, "you're not good enough" is exactly what they're telling us most of the time. You're not young enough, or lovely enough, or enough like a refugee from a sexually conflicted mid-20th-century novel, the ads whisper; but buy our clothes, and maybe, just maybe, you could be. It's hard not to feel a tiny bit pleased when it turns out that these practised emotional abusers have accidentally been seducing the wrong mark. Fallen soap actor, high-level drug runner or street soldier, we've all got aspirations – and why should some guy in the rag trade get to decide whether you're good enough for the high honour of longing to wear the T-shirts he churns out?