I have seen one successful local restaurant go bankrupt in a matter of few months because of negative review. As a matter of fact, it wan't even an official review except for rumors that was spread giving birth to doubts about the cleanliness and quality of the food they were serving.
The rumor was that they serving reheated left over stir fried noodles (Their main dish) that was why they were serving double the amount for a lesser price. When actually they were able to do that was because they were making their own noodles instead of purchasing it so they can give larger servings for a cheaper price. But the rumor spread really fast since it was a small town where everyone knows everybody.