They can also steer consumers in the wrong direction, especially when the review is fake.
The Better Business Bureau, Consumer Reports and even the Federal Trade Commission are warning consumers to be wary of online feedback and reviews of products and services.
For example, the BBB said some companies may hire writers to stack websites with positive comments about a product or negative reviews about their competitors.
"It's bad business to do that because it's dishonest, it's a disservice to consumers and it's also deceptive," Howard Schwartz, spokesperson for the BBB of Connecticut, said.
"I guess it's not that surprising," Trevor Law, an online shopper said. "People are gonna do anything to sell things."
Spotting a potential fake review can sometimes be easy if you look at its wording, according to Schwartz.
"It's not practical that somebody would write, 'this product integrates seamlessly into my life.' Those are market speak words," Schwartz said.
Most consumers won't make repeated use of a product's complete name in a review.
"If you're reading it and someone's talking about how great and wonderful it is and it's life-saving and whatever, you might need to take that with a grain of salt," Evelyn Mackenzie, an online shopper said.
Yelp.com is a popular consumer review website.
A spokesperson for the company said it filters reviews using its own automated system to protect consumers and business owners from fake or malicious feedback.
TripAdvisor.com, another widely-used consumer feedback site, says it also systematically screens reviews and relies on its users to report suspicious content.
The best way to get a feeling for a product is to read a variety of reviews from different sources, according to Schwartz.
(Copyright © 2012 NBC Universal, All Rights Reserved)