Three clean-cut young Americans are sitting in a diner. One is wearing spotless white new Converse trainers and keeps reaching under the table to wipe them. His two friends, sitting across from him, exchange a glance and start mocking his doomed fastidiousness. Then one lifts a foot and deliberately plants the dirty sole on his toe. Her boyfriend gives the Converse-wearer a shrugging, get-over-it look. The Converse-wearer thinks for a second, then leans across the table and punches him in the face. As the boyfriend, unconscious, slides down his seat, the Converse-wearer gives a satisfied smile and takes a celebratory sip.

It's not your usual shoe shop advert. But then ads for Foot Locker, which describes itself as "the world's leading retailer of athletically inspired footwear", rarely are. Other recent commercials for the American-based chain have featured a young man being spanked by his girlfriend with trainers; another young man, blindfolded, identifying specific trainers by smell; another, tougher-looking young man wearing huge, heavy trainers in bed; and young men and women making orgasmic faces as they put on new trainers. "The sneaker addict," as another Foot Locker ad puts it, lets "sneakers dictate 99% of his actions… The sneakers he wears communicate a million more messages than his mobile… He makes sure nothing gets in their way… Experts have named this phenomenon a sneaker way of life."

For decades, as one of the inventors of this "sneaker way of life", Foot Locker has successfully maintained a dual identity. On the one hand, there is its folksy American name and its old-fashioned logo of a black and white striped basketball referee, hands sternly on hips. On the other, there is Foot Locker's advertising: this sells brashness, competitiveness, obsessiveness, insatiability.

Compared with trainers, other types of shoe have been potent symbols – think of high heels or brogues – but never with quite the same intensity or ubiquity or controversy. "At the juncture of the sneaker, a host of cultural, political and economic forces meet, collide," wrote the African-American sociologist Michael Eric Dyson in 1993. "Black cultural preoccupation with style… the commodification of the black juvenile… rapacious consumerism… cultural and personal narcissism… the expanding inner-city juvenocracy… illicit criminal activity… The sneaker reigns as the universal icon of the culture of consumption."

Worldwide, Foot Locker Inc has around 3,400 shops (constant openings and closures keep the numbers fluid), and in Britain about 65, mostly in London and the south-east. Usually, these are orderly places – more orderly than you might expect from the company's advertising. In the showpiece, three-floor branch on Oxford Street, well-built young staff in black and white stripes patrol the tidy aisles. Unusually polite for central London retail, they are also watchful, eyes on the wall displays, with their garish shoals of trainers, from slim and retro to bulbous and futuristic, from Adidas to Puma to Nike, from £30 to £170.

"The target customer of Foot Locker worldwide is a young male, aged 12 to 20," the company says, in one of several guarded and anonymous email responses to my request for an interview. But the Oxford Street shop's customers are more eclectic: middle-aged men, pairs of teenage girls, parents with young children, couples in their 20s. Some customers are in cheap sportswear, others look smart and prosperous. Everyone, even the occasional clusters of teenage boys, all jostle and jittery swagger, picks the trainers off the wall displays delicately, even reverently, holding them by the heel. The most expensive ones are on the highest shelves; to deter shoplifters further, the only decoration on the shop window is a large sticker saying that CCTV is operating "for your safety and to help prevent crime". On the days I visit, no punches are thrown.

But this Foot Locker branch, and others in Britain and elsewhere, can be less calm. Two months ago, at lunchtime on Boxing Day, Seydou Diarrassouba, an 18-year-old from south London, bled to death beside a traffic barrier a dozen yards from the store, surrounded by a panicky police cordon and a huge, restive crowd. According to the police, he had been involved in a confrontation with other customers inside the busy shop – it was the first day of the sales – which climaxed with him being fatally stabbed in the heart.

Last month, Thulani Khumalo, a 20-year-old man from Haringey in north London, was charged with the murder and remanded in custody until 11 April. Another seven men, aged between 16 and 23, remain on bail, having been arrested as part of a continuing investigation into the killing.

Apart from a tiny twist of police tape still attached to the traffic barrier, the Foot Locker and its environs show no trace of the Boxing Day horror. Yet on the internet and in newspapers, conclusions have already been drawn. "Violence does attach to trainers and to the environment in which they're marketed and sold," commented the novelist Howard Jacobson on 31 December.

Looting in Oakland, California (above, left) and Montreal (top) in 2010. After the Boxing Day row in Oxford Street, Seydou Diarrassouba, 18, bled to death (above). Photographs: AP; The Canadian Press/Graham Hughes; Bimal Gautam

In last year's English riots, Foot Locker was singled out. On the night of 7 August, hundreds of looters converged on the branch in Brixton, south London. For more than six hours, as its cheery sign continued to glow in the darkness, the shop front was battered and ripped open, and looters shuttled back and forth from a crowd gathered outside. A man in the crowd, voice tight with excitement, shouted: "Run! Run! Run! Get your own!" One teenager carried out eight boxes of trainers. Another looter was 70 years old. The stealing stopped only after the shop was set on fire. Afterwards, the pavement outside was strewn with single display shoes and empty blue and white Adidas trainer boxes.

Branches were also looted in Manchester, Birmingham and Dalston in east London, where almost all the surrounding shops were left untouched. A few news reports briefly noted this pattern. But there is an untold story of disorder at Foot Locker stores that goes back much farther than last August.

In Dublin in 2006, a branch was looted during a riot between unionists and republicans. In Paris in 2007, during a confrontation between police and black youths over aggressive policing, a chant suddenly went up: "Foot Locker! Foot Locker!" Shortly afterwards, Associated Press reported, at the shop near the Gare du Nord railway station, "Youths broke windows… reaching through the shattered glass to grab boxes of shoes. Passersby also joined in the looting."

In Oakland, California in 2010, also during a riot sparked by police behaviour, a Foot Locker was looted with such brazenness that one thief, immortalised on YouTube, tried out his newly acquired trainers by shuffling slowly backwards and forwards on the pavement outside, store tags still dangling. In Montreal the same year, there was another Foot Locker ransacking as ice-hockey fans celebrated in the street after a play-off victory.

You could see such incidents as simply a mindless ritual. Or you could see deeper social forces at work as well. After the Montreal looting, on the trainer obsessives' website nicekicks.com, a discussion thread hinted at the latter. "Foot locker been feeding on us for a long time… now a lil pay back," wrote hahaa. BlaqINK wrote, "As long as nobody is hurt... footlockers a billion $$ business don't worry they'll be alright." Russ wrote, "[I] use to work for footlocker... they dont care [about] you so I dont care about them im glad this happened."

Alex Hiller of Nottingham Business School suggests the sort of consumerism represented by Foot Locker and trainer culture is increasingly in tension with economic realities. "The trainer industry is targeting very strongly young people who don't have much disposable income" – because of the current downturn – he says. Yet, "Trainers have become a very aspirational product. We all remember being bullied for wearing the wrong trainers at school. It's inconceivable for some people not to take part in the trainer game. If they can't buy those things, they've got to find other ways of acquiring them. And when consumerism turns criminal, sometimes there is an element of resentment, for example at the mark-ups on products. With the recession, that sort of resentment is increasing."

The store mark-up on trainers is typically 100%. Even in better times, the resulting prices made some people take trainers more seriously than many other purchases. In 2000, after the BBC1 consumer programme Watchdog suggested that some Nike Air Max 95s costing £100 – expensive for trainers then – had faulty, squeaky soles and could be exchanged at the shops where they had been bought, a Foot Locker in Leeds was besieged for two days by dissatisfied – and opportunistic – Nike owners. When staff refused to exchange the shoes, police had to be called. There were brawls and seven arrests.

On other occasions, it is the supply of trainers that causes confrontations. One of the ways companies such as Nike create demand is by releasing limited numbers of trainers to limited numbers of shops. Foot Locker, because of its size and status, is almost always one of these chosen outlets. Last year, three days before the Oxford Street stabbing, the release of a particularly sought-after model of Air Jordans in America led to stampedes at several malls. In Burlington, New Jersey, "Foot Locker opened at 7[am]," a witness told the local TV news channel WTXF. With more than 100 people competing for eight pairs of shoes "it was a free for all. People were showing up with guns… A couple of gentlemen walked up and said, 'If I don't get a pair of sneakers, I am going to spray the whole line.'"

In Oregon in July 2008, a lorry carrying thousands of pairs of new Nike trainers collided with another truck, injuring both drivers and killing a passenger. According to the Oregonian newspaper, even while emergency services were at the scene, "several people" tried to steal some of the shoes that had spilled across the road.

The launch of the Jordan Melo M8 at House of Hoops by Foot Locker in Harlem, New York, in October last year. Photograph: Getty Images

Originally, the trainer was invented to promote relaxation rather than manic acquisitiveness. According to Tom Vanderbilt's The Sneaker Book (1998), Dunlop's Liverpool Rubber Company helped conceive them in the 1890s as canvas and rubber "sand shoes" for beachgoers. In 1974 the American retail giant Woolworth established Foot Locker, the first shoe chain devoted to sneakers; by 1979 it had almost 100 branches.

Late-70s Britain took to trainers with a similar intensity. In Liverpool, writes Shawn Smith in the 2003 essay collection Trainers, "A small-scale, black economy began to revolve around the demand for designer footwear… It mostly revolved around gangs of young men who went to and fought at football games… 'casuals'." Then, as now, youth unemployment was high and rising, but hard times only made the suddenly proliferating trainer styles more seductive. And what could not be afforded could be shoplifted: "Many of the Adidas trainers sported by scousers were 'acquired' on trips to various European countries," supporting the Liverpool team, writes fellow Trainers contributor John Connolly.

During the 80s and 90s, trainer fetishism grew from a subculture into the dominant culture of young footwear fashion. Endorsements by rappers and sportsmen, advances in shoe technology, more informal dress codes, modern ostentatiousness and materialism – "the sneaker way of life" emerged from and furthered all these trends. Between 1982 and 1995, sales of sneakers nearly doubled in the US. In 1990 Foot Locker arrived in Britain.

The mainstreaming of trainer culture did not remove its lawless side. On the contrary, by the early 90s stories about people being mugged or murdered for their trainers, and about the symbolically charged role of trainers in gang life and drug dealing, were a media staple. In 1996, a face-off between members of rival gangs in a Foot Locker in California was reportedly one of the causes of the murder of the rapper Tupac Shakur.

For all its watchful staff and in-store cameras, there is a hint of resignation in the company's attitude to disorder in its shops. When I asked what lessons it drew from the looting of its stores in riots, the emailed response was: "We have procedures to ensure the safety of our associates and customers in such circumstances." Store employees, the email continued, were given "ongoing training" to deal with "such events". Did Foot Locker think looting of its shops could ever be totally prevented? "No, but good communication with local [law and order] authorities can help to maximise safety and minimise losses." When I asked whether the company felt the "sneaker way of life" had any broader social downsides, I received no reply.

Staff in the shops repeatedly say company policy forbids them talking to journalists. Foot Locker's PR companies, Hill + Knowlton and Frank PR, send countless holding emails, then finally suggest that a brand manager in the US head office might be able to talk on the phone. Then Hill + Knowlton call to say that he is on "annual leave".

Foot Locker's safety-first approach to its reputation has echoes of how the designer label Burberry protected its own a decade ago, after the actor and cocaine addict Danniella Westbrook and other unwelcome, usually working-class customers became associated with its clothes. Someone who used to work at Burberry recalls: "We didn't talk about it [in public]. It was never even acknowledged. Not acknowledging it meant the 'chav' thing didn't travel."

Yet Robert Clark, a veteran analyst for Retail Week Knowledge Bank, says that for a chain store with good insurance, being looted can be double-edged. "Your security director might be appalled, but your marketing director might think you've achieved something." In one sense, mobs of looters at your stores sends the same message as mobs of shoppers: people are desperate for your goods.

But a reputation for regular trouble risks scaring off most customers. So, more subtly, does too relentless an association with streetwise young male shoppers. "It's a fine line for Foot Locker," Clark says. "They want to be a bit edgy, but if they become too edgy, parts of their customer base, such as older people, may increasingly go elsewhere."

There is not much sign of that happening yet: in 2010 and 2011, despite the disorder at Foot Locker stores, annual profits were up, at close to $200m. But lasting damage can sometimes be done by looters. Six months on from the 2011 English riots, the Brixton branch remains boarded up, sections of wall still blackened from the fire. The premises are to let.

Such closures matter because in the US, saturated with trainer outlets, the company is reducing its number of stores; Europe has been earmarked for expansion instead. But around the world Foot Locker must contend with economic stagnation, internet retail and competition from discount clothing chains and supermarkets. In Britain, sales per square foot – the key measure of retail performance – are over a third down from their peak in 2003.

Vanderbilt describes the trainer as "the emblematic product of the late 20th century" – made by cheap labour, expensively marketed, compulsively purchased. In the 21st century, there are signs of that dominance slipping, thanks to the formal shoe revival, the fashionability of hiking boots and work boots, the renewed appetite for Doc Martens and a visible slowing down in the evolution of the trainer itself.

On the wall displays in Foot Locker and other trainer shops these days, unlike in the 70s, 80s and 90s, there are few new shoe designs to bewilder or dazzle. Increasingly, retro styles rule. Trainer prices, except for the limited-edition, luxury brands sold elsewhere in designer stores, have barely risen for 10 years. After four decades, Foot Locker's "sneaker way of life" may be losing its power.