Yelp users, who flock to the platform known for its reviews and recommendations, should be on the lookout for astroturfing — the creation of fake reviews to make a business look more popular. Andrew Harrer/Bloomberg via Getty Images hide caption

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Patient reviews of doctors tend to focus on non-medical issues like wait time, billing and front office staff. Mahafreen H. Mistry/NPR hide caption

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A health inspection grade is posted outside a Manhattan eatery. In several cities, Yelp users can now find out how a restaurant scored on its health inspection well before they walk through the door. Mario Tama/Getty Images hide caption

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A new study finds restaurants that face close regional competition are more likely to post fake positive reviews for themselves and negative reviews for competitors. Jeremy Brooks/Flickr hide caption

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A sting operation involving a Brooklyn yogurt shop was part of an investigation by New York's attorney general that found companies had flooded ratings websites with fake consumer reviews. hide caption

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Customer review websites like Yelp have exploded in the last few years, but are negative reviewers at risk of inciting the litigious wrath of angry business owners? Richard Vogel/AP hide caption

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