> the rough idea is that if, say, Alice spoke to Bob for a long time and then Alice also spoke to Carol for a long time, then Bob and Carol are more likely than

> the rough idea is that if, say, Alice spoke to Bob for a long time and then Alice also spoke to Carol for a long time, then Bob and Carol are more likely than not to speak for a long time too. This is not how collaborative filtration works. If Alice independently spoke to Bob and Carol for a long time, and Dwayne spoke to Bob for a long time, then chances are Dwayne may speak for a long time to Carol.