My friends and coworkers say I’m nuts having you here, of course,” laughs Elizabeth, the straight-talking, 26-year-old Californian stranger in horn-rimmed specs who’s my host for a spring city break in New York. “Inviting a complete unknown off the internet to stay in my small apartment... they say you’re out to rob me. But there would be much easier ways to do that, wouldn’t there?”

Hospitality networks — communities set up to enable travellers to share the home of a foreign host — are nothing new. Launched by the Denmark-based American Bob Luitweiler in 1949, the United Nations-recognised Servas (www.servas.org ) had the lofty aim of realising Gandhi’s maxim: “The best way to find yourself is to lose yourself in the service of others.”

But Servas, and its contemporary Pasporta Servo (www.tejo.org/eo/ps ), a hospitality community for speakers of Esperanto, functioning as something of a foreign-exchange programme for adults, required a lengthy registration process, membership fee and minimum four-week notice period of a home stay.

Then, networks like the Hospitality Club, which now has 250,000 members in 207 countries, found a happy home on the web. Less formal propositions, these sites were largely the purlieu of backpackers and gap-year travellers, attracted by the twin benefits of saving precious cash and “living like the locals”.

But it was in 2004, with the launch of The CouchSurfing Project, that a verb was coined and a mainstream travel trend born. Couchsurfing.com was the brainchild of Casey Fenton, an American web consultant who, after buying a bargain flight to Iceland, realised that he had no interest in spending his hard-earned greenbacks on “rotting in a hotel all weekend playing Mr Tourist”.

After a bout of beard-scratching, Fenton alighted on the idea of using the random networking potential of the internet to spam a couple of thousand Reykjavik students, asking whether they’d put him up on their sofas and show him around their home city.

The same year, Fenton launched the CouchSurfing Project. The website broadened its focus to online chat and a shared passion for travel, and with several thousand recruits joining the project’s 200,000 registered users each week, Couchsurfing.com is now an undisputed phenomenon.

“The people who come to stay with us come from all walks of life,” says Elizabeth later, as she hands me a cup of camomile tea. “We’ve had a gay German couple in their fifties, lots of thirtysomething couples, as well as younger travellers.

With the older surfers, it’s as if they’re looking for something a bit different to the anonymity of a hotel.” Elizabeth, a nurse, and her boyfriend, Alex, 28, a PhD student (pictured, left), typically house two or three couchsurfers a month, “although, being in New York, we get so many requests”.

I have the distinction of being their first couchsurfer to elicit a profuse round of apologies before even setting my knapsack down on the well-padded beige futon. It’s 11pm on the day of my arrival and for the previous three hours I had been left sitting in an overpriced Upper West Side Italian restaurant, pushing polenta around my plate and tipping back house merlot.

On the plus side, Elizabeth and Alex don’t inhabit the sagging Harlem tenement coloured in by my wild imagination beneath the cover of an airline blanket. My couch lives in a noble American townhouse on a tree-lined street in the shade of the monolithic American Museum of Natural History.

I also wonder, as I stare into the dazzle of Elizabeth and Alex’s mile-wide smiles, whether I should blame myself for my long spell battling the gaze of a rank of insistent waiters. True, there was no sign of the promised key waiting beneath the plastic plant pot on the stoop, but perhaps I shouldn’t have foolishly sent a text to announce my arrival.

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