Do We Really Have 30 Mutual Friends?
Researchers at the University of British Columbia designed a study to show just how vulnerable social networks on sites such as Facebook are to infiltration that can be used for dark purposes. Facebook is known to list the mutual friends of individuals who may have sent a friend request or who show up on the suggestions list of its users. However, the researchers found that if they created fake profiles and added ~5,000 people as friends, they had an acceptance rate of 19.3 percent. However, when the Socialbots they designed reached out to the friends of those people that they had connected with, the requests were accepted 59.1 percent of the time, meaning that people were three times more likely to accept requests from people they didn’t know if they had one mutual real friend in common.
UBC researchers also recognized that social networks offline work in the same way in terms of being built on trusted relationships, a concept called “triadic closure” that claims that ties between two nodes (or two friends on Facebook in this case) that are in a network together can can lead to a relationships with a third that one of the other nodes has a connection to. In this case, even though the connection between the Socialbots and the real profiles were not necessarily strong, they still resulted in a mutual friend accepting a request from the Socialbots.
http://www.huffingtonpost.com/2011/11/02/facebook-mutual-friends_n_1071413.html