Until a few months ago, Neha Shah of Holly Springs, N.C., trusted the hotel reviews she found at online sites such as tripadvisor.com. After all, they came from fellow travelers.

But after a disappointing stay at a hotel in Zurich, Switzerland, that got glowing reviews, she's having second thoughts about the online site's value.

"A lot of emphasis was placed on the service of the staff and how friendly they are," says the 37-year-old writer. "But the service was not consistent."

And a much-ballyhooed breakfast turned out to be a huge disappointment. "Everyone who reviewed the hotel went on and on about the variety, and it simply did not exist."

Tripadvisor's home page promises "unbiased reviews of hotels, resorts and vacations" from thousands of real travelers.

But Shah now suspects that some postings she read might have been planted by hotel staffers intending to bolster business. Looking back, she recalls reviews that "read like brochures in many cases."

She might be on to something.

As Web sites such as tripad visor.com and igougo.com grow in popularity and influence, Web site executives say hoteliers are going to greater lengths to make sure their properties are reviewed favorably — from encouraging guests to post positive reviews to posting glowing reviews themselves under false names.

"It's happened many times," says Jonathan Haldane, founder and chief executive officer of zoomandgo.com, a travel site that posts user reviews. "As part of our due diligence, we'll phone (a reviewer) to check on them and find it's actually someone in the hotel marketing department posing as a guest."

Haldane says it's often easy to spot the planted reviews: They have a gushing quality that just doesn't ring true.

"Hoteliers have a tough time saying anything bad about their own properties," he says. "There's a tone to them, and our staff is trained to look for it."

Unlike some other sites, zoomandgo.com requires reviewers to submit detailed personal information, including their names and phone numbers. Every review that comes into the system is read and vetted by an employee.

Even so, "some (fake reviews) obviously have slipped by," Haldane says.

The cat-and-mouse game with hoteliers also goes on at igougo.com.

"It's not like you can keep (hotel insiders) from posting," says general manager Calvin Evanoff. Still, the site usually catches the fakes, and if it doesn't, the site's members do, he says. "When they see content that doesn't make sense, they let us know. That's the beauty of the community."

Tripadvisor marketing chief Christine Petersen also cites users as a major deterrent to hoteliers who try to game the system.

Petersen notes a case in which a hotel sent guests e-mail offering them cash if they'd give it a positive review. Within hours, tripadvisor users had forwarded the e-mail to the Web site, which deleted the bogus postings that had come in that morning and posted a notice warning of the hotel's strategy.

"We do not approve of any kind of incentives," she says. "Nor do we approve of any kind of soliciting for positive reviews."

Even when reviews are honest, they're not always helpful.

Consumer Reports, which examined online hotel review sites in its March issue, says that "a lot of information (posted by users) is just plain wrong."

Some users such as Chris Pool, 40, of Charlotte, N.C., a devotee of tripadvisor, says he's struck by how often reviewers will disagree.

"One posting says how great everything is, and the next posting says it was the worst place ever," he says. "How can there be such a difference of opinion?"

He believes that Europeans tend to have lower standards than Americans, so they rave about places that are only so-so.

"I often discount the reviews of non-Americans on tripadvisor," says Pool, a drainpipe salesman who travels often.

Still, despite such flaws, many travelers swear by the sites.

Steve Gunn of Seattle says he often sees postings that "appear just a bit too Pollyannaish, but I've learned to look beyond those."

Instead, the 45-year-old sales manager zeroes in on the negative reviews of hotels that he's considering.

"The best value (the sites) provide is warnings from travelers who have had a bad experience. Admittedly, they could be planted by competitors. But why take the chance?"

Elaine Gause, 42, of Salt Lake City, says she takes both super-positive and super-negative reviews with a grain of salt. But that doesn't mean the sites are worthless.

"My method is much like the Olympic figure skating judging: Discard the highest and lowest opinions and average the rest," says the CEO of Girl Scouts of Utah.