"Netflix, the online DVD rental service, has said that 40 percent to 50 percent of its rentals can be traced back to its recommendation system.
Netflix's system uses a program called CineMatch, which relies upon having members rate movies on a five-star scale and then offers suggestions based on the similar ratings of others. But Mike Kaltschnee, of Danbury, Conn., who runs a blog dedicated to Netflix and other online rental services, began noticing problems: The system couldn't differentiate between the independent films he likes and the Barney movies his two young daughters prefer, resulting in a mishmash of suggestions no one wanted. So Netflix configured the system to accommodate individual profiles.
There's still a catch, though: You have to rate your rentals for the system to work. 'What you put into it is what you get out,' said Kaltschnee, 40, who prefers Netflix's system to those offered by other online rental services."
Read more about how other companies make recommendations.