"Voluntourism", the international development charity points out, is a growing market in which increasing numbers of school leavers are paying commercial companies for the privilege of working for nothing in some of the world's poorest communities.

In return, they get a good line for the resume, a clutch of traveller's tales and a warm feeling created by the sense of doing something worthwhile while getting a key "life experience".

Some 200,000 British people - of which 130,000 are school leavers - take a gap year each year, spending on average $9,500 each. Unsurprisingly, some report unrewarding placements provided by unscrupulous companies who fail to fulfil their promise of a meaningful role at the heart of a grateful community.

VSO UK's director, Judith Brodie, doesn't pull her punches in condemning such sharp practice. Young people who want to make a difference, she says, "would be better off travelling and experiencing different cultures, rather than wasting time on projects that have no impact and can leave a big hole in their wallet".
The charity, in conjunction with other organisations, is developing guidelines to help would-be volunteers avoid the pitfalls - common-sense points about checking what's involved in the package, along with some aid-world style awareness of the long-term impact of the placement on the host community.

But while there's clearly a need to put a check on the commercialisation and exploitation of well-intentioned desires, the issue raises some rather difficult questions about our relationship with the developing world, and how we go about helping it.

In one sense, the phenomenon of voluntourism is a problem of success, a testimony to the fact that there is now a huge interest, among the young of the affluent West particularly, in the lives and struggles of communities across the globe.

Generating this kind of concern, and whetting an appetite to act on it, was exactly what made landmark anti-poverty campaigns like Make Poverty History such a success.

But a problem that afflicts the aid world more broadly follows quick on its heels. Having generated this energy, how then to harness it in a way that makes a difference?

Charities are all too familiar with the fact that high-profile, high-tragedy crises tend to generate legions of offers from well-meaning members of the public to go and volunteer in the afflicted area, without having the skills or resources to be effective.

South Asia's 2004 tsunami was a case in point - and now, ironically, negative perceptions of a dangerous Sri Lanka mean that VSO's work there is in jeopardy because of a shortage of volunteers.

A second, related complexity concerns the motives for volunteering. Last year, VSO warned that gap year volunteers risked becoming the "new colonialists" if they didn't change their attitudes to the developing world and stop putting their needs above those of the communities they profess to help.

But can the motives for international volunteering ever be pure? Nearly a decade ago, I did my own mini-version of a gap year while mid-career change, with a month's English teaching in a West Bank refugee camp. It was my first trip to the Middle East, for which I paid a modest fee - around £350 ($700) - to cover the costs of the flight, insurance and food.

On the placement side, the scheme would probably have passed VSO's guidelines: a rigorous selection day was followed by training sessions in what work, culture and conditions to expect. Once in the Palestinian Territories, things were well organised and we were well integrated into the community, which seemed, quite genuinely, to appreciate our efforts.

But - if I'm honest - my motives for volunteering were far from pure. Initially what drew me was an inchoate desire to explore that part of the world by getting under its skin rather than floating over the surface like a regular tourist. In fact, voluntourism wouldn't have been an unfair description of what I was doing.

In the event, the experience went much deeper, and launched me on a professional course that I'm still pursuing today, to which the Middle East is central. But the accidental path by which I got there makes me reflect on the muddy waters of the global consciousness of which voluntourism is a part. Hopefully, more and more people will seek a meaningful relationship with the developing world. But as they do so, there will doubtless be more complexities and pitfalls for organisations such as VSO to point out.