Spotting fake online reviews gets trickier

Before you buy anything online, you probably have a look at those customer reviews featured on the seller's site.

But should you believe what you see?

We know that companies often put up fake reviews, praising themselves.

But now, the New York Times reports some companies have been found to be paying real customers to praise their products -- in one case, dropping an item's final cost to free for participants.

"It's incredibly common," said "CBS This Morning" financial contributor Carmen Wong Ulrich.

The Times discovered that a manufacturer of covers for the Amazon Kindle was offering buyers financial incentives to leave five-star reviews. About 300 reviews went up for the product, which was heavily discounted to $10 from $59.99. Customers were then offered a full rebate in exchange for a review. VIP Deals wrote, "We will refund your order... in exchange for a review. ... We strive to earn 100 percent perfect, 'five-star' scores from you."

"This is a very fine line that a lot of folks kind of are on," Wong Ulrich said. "The (Federal Trade Commission) tried to crack down on this, especially in 2009, because there's a big difference between editorial and advertorial. And you must disclose, it's against the law, if you do not disclose that's there's a relationship between the person reviewing and the vendor."

So how can you tell between a fake review and a real one? Check out Wong Ulrich's expert advice on detecting fake reviews in the video above.