Who are the best spreaders of information in a social network? Best connected individuals may not be the most influential spreaders. Instead, location in the network, as defined by the k-shell, determines influence. Click here for more information and dataset 1 and dataset 2: Twitter, Facebook, LiveJournal and full APS collaboration network. Paper: pdf or cond-mat. Press releases: Technology review, Science Daily, Fast company, Science for SEO, Emedia, NSF,India Times. F1000 prime article. Collaboration between Bar-Ilan University, Boston University, Stockholm University, NYU, and CCNY. Nature Physics 2010. (High resolution image and cover, created with the lanet-vi tool)