It was Karl Marx who said: "From each according to their ability, to each according to their need." While the evidence mostly suggests that communism doesn't really work, the idea of couchsurfing, to which this phrase neatly applies, seems to be going from strength to strength in creating a global, trusting community of travellers.

Couchsurfing.com was first conceived in 2000 by the American Casey Fenton. Having obtained cheap flights from Boston to Iceland, he decided rather than finding accommodation he would randomly e-mail 1500 students at the University of Iceland asking for a place to stay. He received more than 50 offers, and couchsurfing was born. It was launched as a public website in 2004 and today has, according to its home page, 777 346 members worldwide, spread across nearly 50 000 cities in 230 countries.

The idea is very simple. Members offer free accommodation, and also enjoy the same hospitality when they themselves are travelling. At its most basic, this can be, as the name suggests, nothing more than a couch to sleep on, but the main point about it is that it is completely free. To join, all you need to do is set up a profile on the website, outlining a little bit about yourself and what you can offer. It really is that simple; next time you are travelling, simply search on the site for couchsurfers where you are going, and ask them to host you.

Nine, a journalist and project worker from Edinburgh, has been heavily involved in couchsurfing for a number of years. As a single woman living alone, she embodies what one might consider to be the highest risk category, but she says she has never had a bad experience. "The worst thing that ever happens is I host someone who's perfectly nice but who I just don't have a lot to talk about with." However, she emphasises that this is a rarity.

The key is to check out someone's profile, where you can gauge how much you have in common, and thus take a guess at how well you are likely to get on. Also on your profile is a list of references, which will hopefully be a list of nice things people have said about you. It's obviously preferable to host or stay with someone who has a lot of positive references; however, Nine has taken a chance on people who are new to the site and have yet to get any references, and she says this has always paid off. This embodies the community ethos of couchsurfing, with a view that everyone has to start somewhere.

When you mention couchsurfing to people, the first thing they ask is "Is it safe?" It seems to me that one of the main things behind the philosophy of couchsurfing is learning to trust people.

Lucan, a couchsurfer from Montana, United States, stayed with someone who was out of town when he arrived. In fact, he never met his host at all; he was told where the key had been left, and he let himself in and out. This level of trust is, however, a little extreme. Nine always meets her guests in town, and never arranges to hand over spare keys with directions if she is unable to be at home herself. She has turned down people who were arriving when she was working, and is a great believer in trusting her instincts. "Even if there's the tiniest thing that bothers me, I'll say no - I expect this is generally to do with how we'd get on rather than their potential for robbing me of everything I own."

According to Ericka, an English teacher living in Istanbul, one of best couchsurfing communities is in Sofia. "The CS community in Sofia is the tightest I've experienced and everyone there takes the CS philosophy seriously." Ericka first heard about couchsurfing from a fellow traveller in Hong Kong, who suggested it as a way to travel on a budget. "At first I thought it was just a way to allow me to travel more cheaply but couchsurfing is infinitely more than that."

Ericka, like many other couchsurfers, not only offers a place to stay, but is also involved with couchsurfing in a more social way. In fact, if you aren't able, or simply don't want to host people in your home, you can still join the site and be available to meet couchsurfers in your city for drinks. When travelling alone, or even if you're with friends but new to a city, it can be a wonderful thing to meet with someone who knows their way around, and can recommend things which the guide books miss out, not to mention being a nice way to make friends.

There are, of course, horror stories. Ericka, who stresses that she has never had a bad experience herself, met a 19-year-old girl from New Zealand who had just been thrown out by her first ever host. "It was her first time couchsurfing, so she thought she would be extra polite… and do a deep clean of [her host's] kitchen (which is unnecessary in couchsurfing). When her host returned, she freaked on the girl because she had used toxic chemicals while cleaning and that was against her environmental mindset."

Ericka is clear on what action should be taken in such an instance: "In a case like this you need to report the host. No one deserves to be yelled at and kicked out over something like that."

Sadly, my own experience of couchsurfing was no better. In the interests of research, two friends and I found someone to host us in Istanbul. It is a lot easier to find accommodation when travelling alone, so we were lucky to find someone who was able to host all three. Unfortunately, late at night on the day before we were due to arrive, our host cancelled by text, leaving us forced to look for alternative dwellings.

Although inconvenient, and rather thoughtless of her, it must be said that the main annoyance of this was the fact that we had expected free accommodation, and now were saddled with a bill for a hostel. However, since the idea was that we were getting something for nothing, there was nothing to do but to respect our host's wishes.

However, couchsurfing is a largely positive experience. The idea of offering hospitality to a stranger and expecting nothing in return is not a new one, but is certainly one which has fallen out of favour; couchsurfing seeks to reconnect people with the world around them, and to silence that suspicious, capitalist voice which asks what's in it for you.

Nine puts it another way: "I don't ask people to do anything, but often we'll wind up sharing meals, and a bonus is that sometimes guests will give you a small gift or do the washing up. I can't stress how much I appreciate the latter."