At the vanguard of the Internet revolution are two computer scientists from Minnesota who are pioneers of Collaborative Filtering (CF). CF is a technology that enables companies to understand their customers and in turn sell products, goods, and services with remarkable success. To test CF, John Riedl and Joseph Konstan built two Internet sites, MovieLens and GroupLens, that allowed users to customize their preferences for movies and news. The results were astounding -- MovieLens demonstrated amazing accuracy, almost ensuring that the recommendation would prove enjoyable. In "Word of Mouse," the authors analyze dozens of companies from Best Buy to Amazon to TiVo -- and show what these companies are doing right -- and what they are doing wrong. Riedl and Konstan map out a broad range of strategies that companies can employ to raise revenue, customer loyalty, and satisfaction.