Collaborative Filtering

"Collaborative filtering (Wikipedia's definition: the method of making automatic predictions about the interests of a user by collecting taste information from many users) has been around for a long time (in internet years, that is). Pioneering this space was Amazon.com's recommendation software, which could tell a customer that others who had also bought Rushdie's Midnight Children, appreciated The God of Small Things by Arundhati Roy, too. Amazon.com, which also boasts over 6 million product reviews, states that 'the click-through and conversion rates of recommendations based on collaborative filtering vastly exceed those of untargeted content such as banner advertisements and top-seller lists.' Others have followed; collaborative filtering offerings at iTunes, MSN Music, RealPlayer MusicStore, Napster, TiVo (100 million ratings by users about approximately 30,000 TV shows and movies!), Rhapsody and Barnes & Noble have received plenty of attention."