More and more companies are using Yelp and other online review sites, not to promote their own business but to damage their competitors, according to Whitney Gibson and Jordan Cohen of Vorys in a recent blog post. “Many have become quite good at generating false and misleading content for the Internet, despite its illegality,” they say.

And there’s good reason for this online chicanery. Research shows that for every star-rating change on Yelp, a 5 to 7 percent revenue difference could result.