Customer reviews carry more weight with potential buyers than professional reviews do, a study from Weber Shandwick finds. On average, a consumer will look at 11 peer reviews before making a purchase. "We know consumer reviewers are a powerful force. Now we know that they are the most powerful force. Savvy marketers are the ones who listen to, manage and deploy consumer reviewers to harness their considerable might at the cash register," says Bradford Williams, president the company’s North American technology wing.