Today, interest in networks is growing by leaps and bounds, in both scientific discourse and popular culture. Networks are thought to be everywhere ? from the architecture of our brains to global transportation systems. And networks are especially ubiquitous in the social world: they provide us with social support, account for the emergence of new trends and markets, and foster social protest, among other functions. Besides, who among us is not familiar with Facebook, Twitter, or, for that matter, World of Warcraft, among the myriad emerging forms of network-based virtual social...

Today, interest in networks is growing by leaps and bounds, in both scientific discourse and popular culture. Networks are thought to be everywhere ? from the architecture of our brains to global transportation systems. And networks are especially ubiquitous in the social world: they provide us with social support, account for the emergence of new trends and markets, and foster social protest, among other functions. Besides, who among us is not familiar with Facebook, Twitter, or, for that matter, World of Warcraft, among the myriad emerging forms of network-based virtual social...