Amazon.com attracted at least 615 million visitors annually by 2008 according to a survey. A popular feature of Amazon is the ability for users to submit reviews to the web page of each product. As part of their review, users must rate the product on a rating scale from one to five stars. Such rating scales provide a basic idea of the popularity and dependability of a product.
The review feature is an important and highly influential function for customers and one of the main reasons for amazon.com's success at selling books. Reviews give the reader at least a modest basis for evaluating a given book.