For those of you who enjoyed my post on Maximizing Influence Through a Social Network, or anyone with an algorithmic bent to networking, I recommend reading Steve Borgatti's paper on the Key Player Problem.
Borgatti considers two questions, which are roughly --
(1) Who are the handful of people I should quarantine first to stop a contagious epidemic?
(2) Who are the handful of people I should talk to first to influence a community?
He tackles the technical algorithmic issues head-on, with an eye towards specific issues important to social network practitioners (as opposed to graph theorists). In "Maximizing Influence", Kempe, Kleinberg, and Tardos look at problem #2 above and set it within a more abstract framework than Borgatti's treatment, in order to address computational complexity and approximation bounds.
For anyone looking to turbo-charge his next viral marketing campaign, I recommend Borgatti's paper for a good summary of a useful algorithm.