How Facebook Taught Its Search Tool to Understand People - NYTimes.com

Final paragraphs of a graph search snapshot

"Even without context, Facebook is also trying to approximate real world trust. Its search engine ranks answers to every query by an awkward construct that Facebook calls “social distance.” Its algorithms vet who among a user’s Facebook friends the user is closest to and whose answers the user would like to see at the top of search results. The company is betting on the principle of homiphily: if it is from someone the user likes, the user may be more likely to pay attention to it — and click on the link.
“Psychology,” Professor Nass said, “is cheap tricks to meet your goals,”"

How Facebook Taught Its Search Tool to Understand People - NYTimes.com