SAN FRANCISCO -- In a defining moment for the sharing economy, Airbnb is in funding talks that would value the room- and home-renting company at $10 billion, more than some long-established hotel companies and among the highest valuations for a startup in the country.

The sharing economy refers to a wide range of companies that use social networks and smartphones to offer everything from clothes to cars, with business models that connect those with something to offer and those who want something. Airbnb, for instance, lets people around the world rent out space to those looking for a place to stay, taking a cut of each transaction. Sharing companies have grown remarkably fast, disrupting industries like hotels and taxis and raising a host of thorny regulatory concerns.

Clearly, though, they are here to stay and, based on this deal, could become some of the largest companies in the world.

"Getting things from your peers is faster and cheaper," said Jeremiah Owyang, founder of Crowd Companies, which aims to help large traditional companies adapt to the new sharing economy. "People are doing this for selfish reasons. ¿But it's actually sustainable, this is good news for the planet. It's like healthy food that tastes good."

San Francisco-based Airbnb is in negotiations to raise between $400 million and $500 million, which would be its largest funding round ever. The expected investment is more than double its last cash infusion and would value the entire company at $10 billion. In comparison, Hyatt is worth $8.4 billion, and Wyndham Hotel Group $9.3 billion.

The Wall Street Journal first reported Airbnb's funding Thursday, and a source familiar with the matter confirmed the figures with this newspaper. At $10 billion, Airbnb's value would be matched among U.S. startups only by file-sharing service Dropbox, according to data from Dow Jones and the Journal.

Airbnb, along with ride-sharing services like Uber, freelance sites such as oDesk and online marketplaces such as Yerdle, has managed to help carve out a new economy. But regulators worry that sharing companies may represent a public safety threat -- there are horror stories of Airbnb hosts having their homes trashed, and an Uber driver between rides hit and killed a girl on New Year's Eve in San Francisco. Airbnb has also been criticized for evading hotel taxes.

"That's going to be a challenge for many years to come. There's a hand-to-hand battle in every city," Owyang said. But most consumers do trust the sites, experts say, and many sharing-economy users have replaced traditional hotels and taxicabs with these services.

Jennifer Bigler, of Oakley, has used Airbnb twice for trips with her family to Portland, Ore., and West Hollywood. The views from the home in West Hollywood, she said, were unlike anything a hotel could offer.

"It allowed us to stay somewhere with the amenities we needed as a family and on a budget," she said. "We saved hundreds of dollars."

Since it was founded in 2008, born out of Silicon Valley incubator Y Combinator, the Airbnb marketplace has grown to about 600,000 rooms, apartments and houses to rent, and has facilitated more than 11 million guest stays in about 190 countries.

Airbnb's valuation has quadrupled, from about $2.5 billion when it raised funds in 2012. Private-equity firm TPG is expected to lead the next funding round, although Airbnb has also been backed by Greylock Partners and Sequoia Capital.

Other sharing companies have also piqued the interest of some of the valley's highest-profile venture capital firms. Uber received a $258 million funding round from Google Ventures and TPG last year, and Google also led a $125 million investment into the Lending Club, a peer-to-peer loan website. TaskRabbit, a site to outsource errands and chores, ride-sharing service Sidecar and fashion-sharing company Poshmark have each landed tens of millions of dollars in investments in the last couple of years.

"The numbers that we are seeing are self-validating that this is working," said Stephane Kasriel, vice president of product and engineering for oDesk, which has raised about $44 million. "It's a very hot space."

Sharing economy companies are cheap and efficient to operate -- Airbnb doesn't have to build hotels or pay for housekeeping. With few costs, investors see room for huge growth.

"They don't own any properties," Owyang said. "They don't have to deal with anything." Owyang estimates Airbnb, a private company that doesn't disclose financials, makes about $1 billion to $2 billion in annual revenue.

Silicon Valley has played a huge role in the development of the sharing economy, which largely owes its success to advances in mobile technology, social networks and online payments technology such as Braintree, now owned by PayPal. App-based companies such as Sidecar and Uber only exist because of smartphone technology, and the peer review systems that largely weed out the bad actors on sharing economy sites have been built on top of social networks.

Contact Heather Somerville at 510-208-6413. Follow her at Twitter.com/heathersomervil.