Simon Calder: Strangers in cyberspace – can you trust them?

Get the truth, then go – an inspiring slogan for any traveller, but one that raises an obvious question: what constitutes "truth"? The motto belongs to TripAdvisor, the online community that seeks to democratise travel expertise by inviting every traveller to review their hotel or holiday destination.

You read, for example, that the town of Crawley "is one of the most dynamic towns of its size in the UK, with fine open spaces, good places to eat, drink and party, and some excellent hotels".

Such gushing praise for the New Town in Sussex that embraces Gatwick airport may startle you. It doesn't surprise me, though – not just because I grew up there, but because I wrote the review.

Trust me: I'm a travel editor, and as far as I know the only one to have been born beside the A23 halfway between London and Brighton. Just as the internet makes travel agents of us all, so sites like TripAdvisor make travel editors of us all. Bad news for my job prospects, perhaps, but excellent news for travellers who can conduct the age-old tradition of learning from people who have "been there, done that" with speed and ease. Yet Holiday Which? warns travellers to be wary of website reviews of hotels and resorts: they are not all the work of honest, well-meaning individuals: "Who has written the glowing review – a holidaymaker or the hotelier?" asks the magazine.

An Independent reader, John Thorogood, takes up the theme.

"In order to place a review on the TripAdvisor website you just need a name and an email address. That makes it easy for users to subvert the site or post vexatious and untrue reviews and remain completely anonymous.

"It opens the way for hoteliers themselves to post positive reviews in respect of their own establishments, or negative reviews about their competitors," he says.

TripAdvisor has systems in place designed to detect abuses, but requires neither evidence that the contributor has stayed at the establishment nor any evidence to support the review. "It's possible to write what you like about a place you've never even stayed at," says Mr Thorogood.

Neil Fazakerley, the principal researcher at Holiday Which?, regarded user websites as a great idea, until he visited some hotels that had decent reviews, "and I thought they were rubbish".

He now believes that "a hotel which has bad reviews is probably bad, but a hotel with good reviews might not be that good. Sites are useful for filtering out the worst, but I wouldn't trust them for the best."

His magazine reports (but does not name) a resort that emailed staff asking for their friends and families to post positive reviews from their home computers; it also says a holiday company, again unnamed, offered clients a 10 per cent discount in exchange for a favourable review. Anecdotally, there are reports of hotel groups employing people to do nothing other than masquerade as travellers to boost ratings for their properties and disparage the opposition.

The Unfair Commercial Practices Directive, which comes into force next year, is intended to stamp out firms falsely representing themselves as consumers or criticising rivals without justification. But the legislation will have no effect beyond the UK, nor outlaw other forms of manipulation such as patrons urging guests to write up positive reviews, perhaps after a drink or two on the house.

With millions deciding their travel plans on the basis of reviews by strangers in cyberspace, you can see the incentive to boost an enterprise's standing. Even a straightforward traveller's information exchange, such as the long-standing Thorn Tree from Lonely Planet, is open to manipulation.

Some travellers' questions have a straightforward answer; an example from this week is: "Can I get a cargo ship from Cuba to Costa Rica on 2 or 3 November?" No, you can't, silly. But another traveller's query, about the mosquito menace in the Kenyan resort of Mombasa, could invite mischief; a local tourism chief might understate the problem, while it would suit a rival destination in a different part of the Tropics to exaggerate the dangers.

Yet a recent survey found that travellers trusted online review sites much more than they did travel agents – who, like guidebook publishers, are feeling the effects of the expanding pool of expertise. After all, will your local travel agent know more about hotels in Istanbul than a wide range of fellow travellers? And, as a guidebook writer myself, I know that most travel guide assessments are based on a single, random visit when things may have been going particularly well or excessively badly.

Put simply, the more people who take part, the better online review sites become. Malicious or self-serving verdicts will become progressively diluted: the truth, or something close to it, will out.

Even so, anyone considering a large investment like a holiday, who relies exclusively on the opinions of unidentifiable individuals, would be mad not to consult friends, family, guidebooks and a good travel agent. As TripAdvisor warns, users should "take all the reviews posted here as individual, and highly subjective, opinions". And anyone considering a holiday in the fine town of Crawley can contact me privately for some more informed advice.