1 Introduction
Motivated by the phenomenal growth of social networks during the last decade, significant research has been performed on the study of the evolutionary trends exhibited by social networks such as Flickr and LinkedIn [46], technological networks such as those formed by web pages [19] and routers [51] as well as biological and other networks [18]. The ultimate goal in these studies is to interpret the macroscopic phenomena at the network level, relate them with the microscopic behavior of individual nodes and eventually forecast the future evolution of the corresponding networks [46].