When I read about Yelp's (YELP) efforts to crack down on businesses buying positive reviews, it got me thinking about how fake reviews are a huge problem for Amazon (AMZN), eBay (EBAY) and the numerous other merchants that track consumers' views.

One study conducted by Bing Liu, a computer scientist at the University of Illinois at Chicago, found that 80% of the reviews on Amazon had four stars or higher, according to the Christian Science Monitor. He estimates that 30% of online reviews are fake. That number may be low, given the growing importance that businesses place on customers' feedback.

Some businesses have gotten the idea that the Internet is a place "where seldom is heard a discouraging word." Companies are extremely concerned -- and rightly so -- about their online reputations, because unfounded rumors can damage multibillion-dollar brands in the blink of an eye. Consumers, however, need to be suspicious about what they read online, because of the sophisticated ways companies "manage" their reputations.

Reputation Changer, for one, tells advertisers that it can "suppress defamatory posts" and "eliminate negative BBB Ratings from high ranking status," information that consumers might want to know. Reputation.com says it can eliminate "negative material from your top search results," such as "unfair news articles" and "disparaging blog posts."

But far from deterring consumers, negative reviews should be viewed as a positive. My wife has a small side business, and I understand how difficult it can be to deal with the public. Customers may always be right, but they are also occasionally dumb -- and even crazy. Things go wrong in every business. Merchandise gets damaged in shipping or is defective. Sellers sometimes send the wrong product or ship something to the wrong place. Stuff happens.

Good companies learn from their mistakes. Honest ones admit they have them.

Jonathan Berr does not own shares of the listed stocks. Follow him on Twitter@jdberr