Travel sites such as Expedia and PriceLine.com have started closely examining user reviews to ensure that the entries are authentic, Reuters reports.

Sites have begun monitoring each submission with fraud experts and are verifying that users have actually stayed at the hotel about which they submit a review. Yet, even as travel sites add measures to more closely monitor user submissions, dishonest reviews slip through.

"We have certainly seen instances with other properties where insiders have put reviews up for a particular hotel or a particular thing and it's not a legitimate review," said Jeff Boyd, Priceline.com's Chief Executive.

With almost $70 billion spent at online travel sites in 2006, accurate information, including user reviews, is a must if the sites are to retain credibility with users.