Some interesting insight into the effects of Yelp on restaurants from Brad Plumer at WonkBlog:
However, looking more broadly, chain restaurants as a whole seem to have declined in market share as Yelp has grown in prominence. “This suggests,” [Michael] Luca writes, “that online consumer reviews substitute for more traditional forms of reputation.” In 2007, about 50 percent of all restaurant spending, some $125 billion per year, went to chain restaurants. Chains have always benefited from uniformity: No matter where you go, you always know what you’ll get at an Applebee’s or a McDonald’s. Independent restaurants, by contrast, are more of a gamble. But as online review sites like Yelp expand, that’s no longer the case.