“This is the last thing you want to hear when you’re couch surfing,” said my host, Cortney Fielding, a thirty-year-old freelance writer, when I arrived, this winter, at her one-bedroom apartment in the Nob Hill neighborhood of San Francisco. “Couch surfing” refers to the practice of temporarily lodging with a stranger—free of charge, unless you count being incessantly sociable as payment. Fielding and I, along with 3,965,492 others, are members of CouchSurfing.org, a hospitality-exchange network that pairs travellers looking for a place to crash with locals willing to accommodate them or perhaps just meet for a beverage. There are members in every country, including North Korea, Pakistan, and the Vatican, and also in Antarctica. They speak, all told, three hundred and sixty-five languages—Saramaccan, Yapese, Quiché, and Nicaraguan Sign Language, to name some I bet you are not fluent in. The WikiLeaker Julian Assange belonged to CouchSurfing.

Is couch surfing for people who have no friends? How do you know the sheets are clean? What happened to “Never talk to strangers”? Illustration by Nishant Choksi

I do not find the concept of consorting with unknown persons appealing. (Is it for people who have no friends? How do you know the sheets are clean? What is it with people always wanting to get together? What happened to “Never talk to strangers”?) Still, I joined CouchSurfing recently, and I surfed in four cities on seven couches (actually, beds, mostly). Fielding and her husband, Andy Storch (he was out of town on business when I visited), are three-year veterans. “Like most Americans, we have two weeks of vacation, so we don’t get to travel much,” Fielding explained. “If we can’t go to the world, the world will come to us. So, when we’re feeling a little bored, we think, All right, why don’t we have someone from the Netherlands visit? It’s like a blind date where the person brings his toothbrush.” Fielding and Storch, who typically take in guests every month, recently hosted a dumpster-diving couple from Canada and had just said yes to some Australians. (“We’ve never had Australians. We thought we’d check another country off our list.”) And what was the news that Fielding had alluded to when I walked in, intending to spend the night on the latte-colored microfibre pull-out sectional sofa in their living room? “I just came back from the vet,” she said, “and my cat has bladder problems.” I am not a cat person in the most continental of circumstances. “How’s the dog?” I asked of the boxer that was sniffing my suitcase. The dog was fine. And off we went to the apartment of a friend of Fielding’s to watch “The Bachelor” with a group of reality-TV connoisseurs.

Upon joining CouchSurfing, you are instructed to compose an online profile, delineating your philosophy and mission, the skills you can teach others, your favorite music, movies, and books, and so much else that you might as well be applying to college. Members also post photographs of themselves, sometimes hundreds of them. Often, they include a picture of the sleeping accommodations, which range from sofas to sleeping bags, from shared beds to guesthouses. I’d selected Fielding and my other hosts after scrolling through hundreds of profiles, winnowing out those whose narratives included the words “party,” “vegan,” and “free spirit,” and the phrases “I believe in the journey,” “Never stop learning, never stop loving,” and “Burning Man.”

Among those to whom I did not write “couch requests” were “a travelling magician and professional fool” from New Mexico; a sixty-three-year-old gay semi-retired handyman in Pahoa, Hawaii, whose mission is “looking for more nudists” (there are plenty of “clothing optional” possibilities on CouchSurfing); another Hawaiian, this one describing himself as “just a guy who has three acres of land, living in a shipping container house”; a woman in Bozeman, Montana, who declared that her “home is oppression-free. Yay!” and also contains high-speed Wi-Fi; a thirty-one-year-old female “daydreamer” from Berkeley who loves pajamas; a Tarot-card reader in Marfa, Texas; a housewife in Charleston, South Carolina, who owns a pole-dancing studio called Dolphin Dance; a kite-surfing physician (again, Charleston) whose ambition is to start a flavored-envelope company; a freelance photographer in San Francisco who claims she’s had hiccups every day for the past five years; a Savannah, Georgia, scientist who is also a “free man,” doing “whatever I want, whenever I want”; a male in Antarctica who wishes to live as a female; a “lovetarian” who grew up in Doylestown, Pennsylvania; a “proud Bangladexican” (Mexican-Bangladeshi) who likes “exciting things,” by which she means animals, forests, and jumping; an Afghan man, in Kabul, who lists his occupation as “warlord”*; another man, also in Kabul, who works as an aid worker and sometimes as an optometrist; a seminarian living in Vatican City who previously attended the Navy’s flight school and would like to have coffee with anyone passing through the sacerdotal-monarchical state; an empty-nester couple in American Samoa who have two free bedrooms in their house, which is twenty feet from the beach, with “no hot water (who needs it?)”; a twenty-five-year-old Web designer and trucker in Munich whose “perfect day” includes playing football and afterward discussing politics and getting “so mad about it, so we fight with some chairs and destroy the whole bar”; Amin Awad, from Sudan, who loves “modest guests”; an archeologist in Death Valley who assures you that black-widow spiders are gently and immediately removed from her house; a professional vegetable masher in Beijing; a guy in New York City who’s hosted a lot of couch surfers and has had only three who “sucked”; and eighty-four people in Brunei Darussalam.

According to the CouchSurfing Web site, the average age of members is twenty-eight, with more than a third between the ages of eighteen and twenty-four (seven hundred and ninety-three members are between eighty and eighty-nine). Reasoning that these youngsters would never welcome me as a house guest, fearing perhaps that they’d have to get out the defibrillator, I subtracted nine years from my age on the profile. However, when twenty-three-year-old Sydney Provence, a University of Iowa physics grad student, picked me up in her Toyota Corolla at the airport in Cedar Rapids—the first stop on my surfing odyssey—I immediately confessed my misdeed. “To anyone in her twenties,” she said, “forties, fifties, it’s all the same.” As we drove through winter-browned fields and then, for my touristic benefit, meandered through Iowa City, Provence called my attention to local sights. She said that she first couch-surfed four years ago, as a broke college student eager to see Austria but not without a companion. On that trip, she spent Christmas in St. Valentin with a girl her age and the girl’s mother, eating homemade holiday treats. Recently, Provence and her younger brother couch-surfed in Costa Rica, where they stayed with a tavern owner, a lucky break for her brother, who discovered that he was of legal drinking age there.

We reached Provence’s house—a clapboard bungalow built in the early nineteen-hundreds, which she acquired with some inherited money two years ago. The house has a wooden kitchen floor convincingly painted to look like a signed Matisse cutout, holographic art created by her father, a little red panic-like button that has no purpose whatsoever, and, best of all, a large downstairs with a daybed (and bathroom) for me to share with her beer-brewing equipment. When I marvelled at how grownup her house was, she observed, “You know you’re an adult when you have separate toilet paper, paper towels, and napkins.” We had dinner at a Japanese restaurant and then stayed up late, gabbing about, oh, you know, molecular beam epitaxy, blackbody radiation, and the Topless Tuesday Pancake Dinners she attended in her undergraduate days, at the University of Virginia.

When I told friends that I would be sleeping in the company of strangers, the second most frequent question they asked was “How do you know you’re not going to be bludgeoned to death in the middle of the night?” The most frequent question was “What about bedbugs?” Regarding the latter, I have not come across a single mention on the Web site of these pests, so, New Yorkers, get over your paranoia. As for safety concerns, a twenty-nine-year-old woman from Hong Kong was raped when she travelled to Leeds in 2009. There have been less dire violations reported, too, such as burglaries and harassment, but Daniel Hoffer, the company’s C.E.O. and co-founder, who is thirty-four, says that, statistically speaking, couch surfing is remarkably safe. “We have had over six million positive experiences, with only a tiny fraction of one per cent negative,” he told me at the groovy new CouchSurfing headquarters, in San Francisco, a double-level aqua-and-orange-painted loft sheltering seventeen couches and two swings suspended from a roof beam.

O.K., but what happens if Jack the Ripper signs up? There are three protective measures, each indicated on a member’s profile. First, for a credit-card payment of twenty-five dollars, the Web site will verify your name and address (which means that a member can be certain she is hosting the real Ripper, and not an impostor). Another feature, “the vouch,” is a sort of seal of trustworthiness conferred upon a member, say, Jack, by another member, say, Mrs. Ripper. Only members who have been vouched for three times have the power to issue such an endorsement. The most helpful security information, however, is the references that hosts and guests are encouraged to write about each other after every rendezvous. According to a 2010 study conducted by researchers at the University of Michigan, the ratio of positive to negative evaluations is twenty-five hundred to one. Still, an astute reader can read between the lines in an assessment like “Jack has an awesome collection of steak knives” or “He can put out a fire really fast.” Given these safeguards, it is unlikely that anyone on CouchSurfing could get away with murder more than once. How comforting.

My next hotelier, cicerone, and instant buddy in Iowa City, Deborah Yarchun (age twenty-six), was neither verified nor vouched for, but she had thirteen gushing references. A strawberry blonde dressed in black who rides a unicycle and does micrography, making drawings composed of tiny words, Yarchun is pursuing an M.F.A. at the Iowa Playwrights Workshop. Over morning coffee at the Prairie Lights bookstore, she explained that she joined CouchSurfing after she moved to Iowa, in 2010, and missed having roommates. “The first time I lived alone, I lasted three days before I bought a hamster,” she said. “CouchSurfing is perfect, because I can share my space a day at a time.”

She went off to her classes, lending me a set of keys to her apartment, a one-bedroom appointed with furniture from the annual Iowa City-sponsored garage sale and a black futon from Walmart that has been transiently occupied by, for instance, a student from Lyons, France, in town to work on a paper about Grant Wood; a motivational speaker who visited after he and his fiancé parted ways (“His spiel was about balance”); and, most recently, by me. That night, before attending a tech rehearsal for her upcoming play, we had dinner at Hamburg Inn, a diner famous for pie milkshakes and for being a mandatory political stop for candidates during the Iowa caucuses.

For all this generosity, what did I offer in exchange? Many guests cook a meal, clean the house, or walk the dog. I gave Yarchun—and everyone I visited—a book, a box of chocolate cookies, and an authentic hundred-trillion-dollar bill from Zimbabwe. If the bill had been worth more than the pittance I paid for it on eBay, I would be kicked off the Web site, as would Yarchun for accepting money. “It’s about the exchange of stories, not cash,” Yarchun said, offering up a hair-raising tale about being attacked by seven vicious dogs in Ecuador.

CouchSurfing is neither the first nor the only organized pajama party on the block. Servas, generally regarded as the earliest hospitality exchange, was founded, in 1949, as a means of promoting world harmony (its original name was Peacebuilders). Servas is so archaic—or do I mean utopian?—that not only is it recognized by the U.N. but its members still communicate via postal letters and must be interviewed before joining. (I talked to one couple who had applied for an interview, were informed that it would take six months to be approved, and were now, a couple of years later, still waiting.) Other networks include Global Freeloaders, Be Welcome, Nomadbase, Tripping, Evergreen Bed and Breakfast Club (for those over fifty), Pasporta Servo (for speakers of Esperanto), and the Hospitality Club, which, with more than three hundred thousand members, is a distant second to CouchSurfing in terms of size.

CouchSurfing was the brainchild of Casey Fenton, who is thirty-four, and who told me over the phone from San Francisco that, as a boy growing up in Brownfield, Maine, he’d become fascinated by the concept of free will, cherishing the hope that someday he would have the existential wherewithal to escape his home town and explore the world. Chalk one up for volition: Fenton graduated from high school early and began travelling soon afterward. “I travelled randomly,” he said, “buying tickets that would take me as far away as I could afford to go.” In 2000, in preparation for a trip to Reykjavík, Iceland, he spammed fifteen hundred university students, canvassing for free accommodation. He received between fifty and a hundred invitations, proceeding to bunk with a few of the respondents, and even the family of one. “When else, I thought, would I have an opportunity to stay with a socialite and a nationally known R. & B. star?” he said. Eureka!

Fenton—by training a computer programmer—spent several years developing his travel Web site. In 2004, with the help of Daniel Hoffer and two others, who are no longer part of the team, he launched CouchSurfing as a public company. Its mission was “to internationally network people and places, create educational exchanges, raise collective consciousness, spread tolerance, and facilitate cultural understanding.” In those days, before CouchSurfing had an office, idealistic volunteers, provided with room and board, worked together out of group houses that were rented in It places like Turkey, New Zealand, Costa Rica, and Alaska. The phrase “couch-surf” was in use at the time, but, according to Fenton, it meant to watch TV on a friend’s sofa, lazily flipping through the channels. “We popularized the term and gave it an adventurous association,” Fenton said. “We changed the context so there was a community aspect.”

A small segment of the community became angry when, last August, CouchSurfing accepted $7.6 million in investment. Never mind that the company has used some of the funding to hire computer engineers, or that it converted from a traditional nonprofit to a B corporation, a new type of company that is contractually required to be socially and environmentally responsible. Certain diehards simply do not like doing business with the Man, or even doing business. From their perspective, CouchSurfing’s raising capital is the equivalent of the Salvation Army’s developing nuclear weapons. The discussion group on the CouchSurfing Web site that is entitled “We Are Against CS Becoming a For-Profit Organization” has more than three thousand members. To put this in context, the “Barefooters” group has eight hundred and twenty-eight members; “Pirates!” has four hundred and three; “People Who Like Singing in the Shower” has one hundred and sixty-eight; “Chin Scar!” has fifty-five; “The Cute Guys Club” has eight hundred and thirty-five; and the “Cute Guy Club of Florida” subgroup has one.

Speaking of moola, Bermuda is a swell place to couch-surf. I take it you know more or less what this Manhattan-size archipelago looks like, but, if not, picture a subtropical island, then doctor the picture so that the blue water is bluer and the pink beaches are pinker. Don’t forget the limestone houses painted in Necco Wafer colors, with white ridged roofs designed to funnel rainwater into cisterns. True, you may not find CouchSurfing digs chez Michael Bloomberg, Silvio Berlusconi, Ross Perot, Michael Douglas, or any of the other folks who live in the gated community of Tucker’s Town. If you are as discerning a reader of profiles as I, however, you can be put up in houses that, were they hotels, would receive five stars.

Night No. 1: Cris Valdes-Dapena and Ian Birch. This recently married couple in their sixties—he’s an aspiring clockmaker and paraglider from England, she’s a partly retired real-estate agent from Pennsylvania—welcomed me early one evening to their semi-detached condominium, a handsome white concrete house overlooking Hamilton Harbor and the Great Sound, a panorama I could admire through the sliding glass doors of my bedroom. (I had a marble bathroom to myself, too.) Valdes-Dapena and Birch joined CouchSurfing last year, having heard about it from Valdes-Dapena’s grandson. A few days before my stay, they hosted a sixty-four-year-old former travel agent from Victoria, Canada (“We reverse age-discriminate”), whose mission, as stated on the CouchSurfing Web site, was “to feverishly explore the world before I croak.” He’d been on a gruellingly circuitous journey in order to accumulate frequent-flier miles, and showed up late, conking out almost immediately on the sofa. I had taken a mere two-hour flight, so that night, over an unhurried dinner of spaghetti Bolognese and garlic bread, Valdes-Dapena and Birch gave me the lowdown on Bermuda politics and economics and regaled me with tales of their travels—they have places in Colorado, Mexico, and New York, and have trekked along the Annapurna Circuit, in Nepal, and Camino de Santiago, in Spain. Later this year, they will walk through New Zealand for three months.

I, on the other hand, accepted a lift from Birch the next day to a nearby bus stop. When, half an hour later, on the other side of the island, I stepped off the pink-and-blue-painted No. 10, Andrea Wass, a winning thirty-eight-year-old insurance underwriter, was there to escort me down the steep driveway to her charming rented house. She led me to a room that overlooked a landscaped lawn and, beyond that, a private dock where she keeps a kayak. There were flowers on the bedside table. “You have your own room,” she said. “I don’t include that on my profile, because I’d be inundated with requests.” Wass was transferred by her company to Bermuda six years ago, so by now the visits from friends and family have ebbed. (She travels regularly to the States.) Wass said that she misses having guests—and that, I suppose, is where I came in. The night I arrived, we dined with four delightful expat friends at a nice hotel restaurant, where I learned, among other things, that in 1992 a construction crew working for Ross Perot illegally blew up a coral reef so that he could moor his yacht, the Chateau Margaux, at his doorstep. The next day, Wass and I visited a cave, wandered around St. George’s (possibly the oldest continually inhabited English town in the New World), and tooled around the island on her Vespa, I, the terrified passenger, trying to fake blasé.