"... error tolerance is not shared by all redundant systems: it is displayed only by a class of in-homogeneously wired called scale-free networks, which include the World-Wide Web, the Internet6, social networks7 and cells8. We find that such networks display an unexpected degree of robustness, the ability of their nodes to communicate being unaffected even by un-realistically high failure rates. However, error tolerance comes at a high price in that these networks are extremely vulnerable to attacks ..."
Watts & Stogatz are instrumental in our understanding of "small world networks" ~ http://en.wikipedia.org/wiki/Small-world_network and Barabasi discovered Hubs (frequency of connections between nodes) ~ http://en.wikipedia.org/wiki/Albert-Laszlo_Barabasi
"... error tolerance is not shared by all redundant systems: it is displayed only by a class of in-homogeneously wired called scale-free networks, which include the World-Wide Web, the Internet6, social networks7 and cells8. We find that such networks display an unexpected degree of robustness, the ability of their nodes to communicate being unaffected even by un-realistically high failure rates. However, error tolerance comes at a high price in that these networks are extremely vulnerable to attacks ..."
Barabasi is important because of this paper, Albert R., Jeong R., Barabasi A, "2000, Nature #406, pp 378-402., 'Error and attack tolerance of complex networks'", (pdf 249Kb) ~ http://www.barabasilab.com/pubs/CCNR-ALB_Publications/200007...
Do not forget Vespignani ~ http://en.wikipedia.org/wiki/Alessandro_Vespignani who applied both the small world network idea and hubs to produce network diagrams showing "spatial spreading of disease" ~ http://www.pnas.org/content/106/51/21484.full