In the brutal world of online commerce, where a competing product is just a click away, retailers need all the help they can get to close a sale.

Some exalt themselves by anonymously posting their own laudatory reviews. Now there is an even simpler approach: offering a refund to customers in exchange for a write-up.

By the time VIP Deals ended its rebate on Amazon.com in late December for its Vipertek leather case for the Kindle Fire, hundreds of reviewers had proclaimed the case a marvel worth five stars.

Fake reviews are drawing the attention of regulators. "Advertising disguised as editorial is an old problem, but it's now presenting itself in different ways," said Mary K. Engle, the Federal Trade Commission's associate director for advertising practices. "We're very concerned."

Researchers like Bing Liu, a computer science professor at the University of Illinois at Chicago, are also taking notice, trying to devise mathematical models to systematically unmask the bogus endorsements. "More people are depending on reviews for what to buy and where to go, so the incentives for faking are getting bigger," said Mr. Liu. "It's a very cheap way of marketing."

By late January, 310 out of 335 reviews of VIP Deals' Vipertek brand premium slim black leather case folio cover were five stars. VIP Deals, which specializes in leather tablet cases and stun guns, denied it was quietly offering the deals. But three customers said in interviews that the offer was straightforward: the VIP page was selling a cover for under $10 plus shipping (the official list price was $59.99). When the package arrived it included an invitation "to write a product review for the Amazon community."

"In return for writing the review, we will refund your order so you will have received the product for free," it said.

Anne Marie Logan, a Georgia pharmacist, was suspicious. "I was like, 'is this for real?'" she said. "But they credited my account. You think it's unethical?"

The merchant did not respond to further requests for comment.

Under F.T.C. rules, when there is a connection between a merchant and someone promoting its product that affects the endorsement's credibility, it must be fully disclosed. In one case, Legacy Learning Systems, which sells music instructional tapes, paid $250,000 last March to settle charges that it had hired affiliates to recommend the videos on Web sites.

Amazon, sent a copy of the VIP letter by The New York Times, said its guidelines prohibited compensation for customer reviews. A few days later, it deleted all the reviews for the case, then it took down the product page. A spokeswoman declined to say exactly what happened to VIP's products, like the Vipertek VTS-880 mini stun gun, which all also disappeared after receiving nearly all five-star reviews.

"I bought one for my wife and decided to let her try it on me," one man wrote in his review.

"We gave it a full charge and let me just say WOW! Boy do I regret that decision."

The New York Times

(China Daily 02/12/2012 page10)