TripAdvisor hits its 50 millionth review – but can they be trusted?

It may be the scourge of many a hotelier, but for thousands of people the review website TripAdvisor has become as much a part of the summer holiday as sun cream and suitcases.

Almost 10 years after publishing its first review, the site is one of the internet's success stories, in traffic terms at least. More than 50 million reviews have now been published on the website, which invites customers to share their experiences of hotels, flights, restaurants and tourist attractions. More than half a million properties have been reviewed there.

When its founder, the American Steve Kaufer, set up the site 11 years ago, unhappy that the only information he could get for a trip to Mexico was from travel agents and glossy brochures, he could hardly have imagined it would become arguably the biggest power-broker in the travel industry. But its ascent has generated more than its fair share of controversy – several hoteliers have threatened legal action, claiming its reviews are inaccurate or deliberately malicious. It is undoubtedly powerful but not, they claim, backed up with adequate responsibility. Vast discrepancies in opinions on the same property have attracted suspicion that overly favourable reviews are the work of hoteliers themselves or their friends, and negative ones are the work of rival businesses.

The Cove Cornwall, which has apartments and a cottage at Lamorna Cove, recently found itself at the centre of allegations that it bribed customers with promises of discounts in return for favourable reviews.

TripAdviser pointed out that it is against its rules for incentives to be offered "in return for reviews" but Lee Magner, the owner of Cove Cornwall, denied any attempt to bribe customers. He accepted the wording on leaflets informing customers of a loyalty card system may have been unclear, but is seeking legal advice to counter suggestions of impropriety. The site also has high-profile detractors – in January, Dragons' Den star Duncan Bannatyne reportedly labelled it "despicable and cowardly" after reviewers criticised a hotel he owns.

But Emma O'Boyle, TripAdvisor UK's spokesman, insists it can be trusted. "We're confident that the vast majority of the reviews are authentic," she said. "We have system tools, and human beings too, in place to verify content for integrity. Owners can reply to negative feedback and we encourage them to do so. If we catch owners misusing the site we make sure they know about it, and businesses understand they have a lot to lose by doing so. We have 40 million unique users a month – if it wasn't reliable, people wouldn't come back."

Same place, different score

Hotel Tropical, Ibiza, Spain

"It was superb! the staff were fantastic and the food was spot on!"

"I would honestly not recommend this hotel to my worst enemy. The security guard shouts abuse at you in Spanish and uses his master key to walk into your room while you're getting changed."

The Bellagio, Las Vegas

"Without doubt the best hotel we have ever stayed in & are already booked to stay again!! Amazing!!! pure 5-Star indulgence, one of a kind!"

"There were vomit stains in the closet. We couldn't do anything to get rid of the stench. We found a used condom in bed with us. Isn't this hotel supposed to have a good reputation?"