The news of another disaster involving "adventure" or "extreme" sports has proved once again that there is a high price potentially to be paid for such adrenaline-fuelled fun. No doubt to the surprise of many regular participants, these activities have again been revealed to be more than just active style statements - they really can kill you, whatever it may say in the advert.
While some participants may brag that this fact only increases the kudos of extreme sports, for the rest of us it must also lead to questions about why people would want to get involved in the first place. More precisely, why would young people with everything to live for willingly put their lives in the hands of total strangers, in increasingly dangerous situations over which they have little or no control?
Dangerous sports are not a new phenomenon - particularly in Britain, which has been producing men happy to risk all since long before Captain Scott went to the Antarctic and didn't come back. What is relatively new, like the Pepsi advert, is the commercialisation of this urge by a growing industry that promises that anybody can do it all, providing they are prepared to pay.
The progress of an activity such as rock-climbing is instructive, and shows how our attitudes towards dangerous sports have changed. Originally the preserve of wealthy young men, climbing saw its greatest popularisation in this country after the Second World War, when groups of mainly working- class northerners took to the local crags and cliffs as a release from mundane factory life. This was the movement that produced the first rock- climbing "stars", such as the late Joe Brown, who developed new techniques by applying an almost professional attitude to their hobby.
Partly because of the scene's financial constraints, however, this burst of interest took place within a distinctly clubby atmosphere, in which rudimentary equipment was shared and young aspirants were literally taught the ropes by older, wiser heads. The emphasis was on acquiring skills through serving something akin to an apprenticeship, in a joint effort to push for ever steeper, more difficult routes.
The ultimate ambition of many such climbers was to get to grips with the world's great peaks, and they would work and wait for years before being considered good enough to take part in a major expedition. Today, while much of the above still holds true at grass-roots level, two things have changed. First, climbing has become fashionable, even sexy, with equipment manufacturers selling the image of beautiful, Lycra-clad bodies. Secondly, it has also become possible to tackle big mountains without having to go through the bother of all that apprenticeship business. These days, you can even get to the top of Everest if you can sign a big-enough cheque. And as the tragic toll of the last 10 years shows, these developments have led to a huge increase in the death rate.
Scuba-diving has seen a similar growth in interest, and a similar commercial drive to make the sport accessible. Where once a course with the British Sub-Aqua Club would take the best part of a year spent in the classroom and swimming-pool before entering "open water", now a course can be completed in a matter of days on a palm-fringed island. "Demonstration" dives, with virtually no training at all, are also available at many resorts.
As a result, the numbers involved in scuba-diving have quadrupled over the past 10 years - to the point at which there are now about 100,000 "qualified" British divers. "The way we work and the way we live is very different now," says Graeme Gourlay, publisher of Dive magazine. "People want to go in and buy a service. The sport has had to adapt, but if you let it be taken over by rampant commercialism then, inevitably, safety is not the only priority. People are there to make money."
If that is the way things are in an established sport such as scuba-diving, the situation with newer, less-regulated sports is more precarious still. The push for ever-greater thrills has led to a loss of interest in the acquiring of skills and a premium being placed on the "adrenaline rush".
"A lot of it is about the macho factor. It's about people trying to make their lives more interesting than other people's," says Pete Muir, managing editor of the thrill-fixated Maxim magazine and himself a climber. "It is also about instant gratification. People want to get their kicks instantly, tick that off the list and go and tell their mates about it down the pub before moving on to the next thing. Most of it comes down to posing."
This prevailing attitude leaves the whole business subject to the laws of fashion, and to an acceleration in the demand for newer, more extreme activities, as people become more competitive with each other. None of these new activities is regulated, not only because they haven't had the time to become established but also because regulation would damage some of the sense of rebellion that is associated with them.
New Zealand has long been at the forefront of these developments - from well-known activities such as bungee-jumping to the until recently more obscure sport of canyoning. The current craze in those islands is known as a Zorb. A mixture of roly-poly and Gladiators, it involves getting inside a large, transparent ball and being rolled down a hill at speeds of up to 30mph. Wicked.
John Adams, professor of geography at University College London, has spent years studying the concept of risk, and on Sunday presents a Big Ideas special on the subject for BBC2. He concludes that the need to do something risky is brought about by the fact that life in general has in fact got a lot safer. "We have a profoundly ambivalent attitude to risk," he says. "All the heroes you find are the risk-takers, then you turn around and find the Health and Safety Executive looking over your shoulder making sure that you are safe."
The best illustration he has seen of this was during a visit to Switzerland three months ago, when he came across a brochure for an adventure sports company that uses the slogan: "Risk Your Life As Safely As Possible!" By contrast, Professor Adams cites plans to phase out the old-fashioned Routemaster buses in London, on the grounds that it is too dangerous to allow people to get on and get off when they want.
"I think, as imposed risks recede - such as the risk of dying in infancy or of an infectious disease, the risk of dying in a dangerous mine or factory, or the risk of being conscripted to die in a trench - then we do seem to find at least a partial replacement in risks voluntarily assumed," he says.
Again, he draws a distinction between a sport such as mountaineering, in which a large number of skills are involved, and something like bungee- jumping, which he compares to a fairground ride. "It looks and feels very scary... but it isn't really." And he stresses that, to the mainly young men who participate in the wilder shores of dangerous activity, these activities immediately lose some of their appeal if they become too tightly organised.
He quotes a recent case in Toronto where police had to crack down on groups of youths who were organising their own car races on public roads in the dead of night.
"I would suspect that if this is stopped, or regulated," adds Professor Adams, "then [these young men] will seek out another activity where they can play by their own rules."
So we can expect that as long as companies seek to appeal to this rebellious streak by supplying an attractively packaged adrenaline rush, then youngsters will keep buying. And posing. And dying.