What is the likelihood of people forwarding on items that they receive in a social network such as Facebook (news items, links, video clips)? What is the likelihood of people responding to messages, or re-tweeting other people's tweets on Twitter?

"The idea we need to explore is this: what is the likelihood that a particular stimulus within a social network leads to a particular response?" says Lieberman.

One of earliest in-depth studies of how social networks function as an ecosystem of influence. As these studies advance, we'll be seeing more science (and proper monetization) behind reaching the influencers.