Acquaintance recommending in local world: Evolving mechanisms of IM user topology

Instant messaging (IM) has become increasingly popular in the past few years. An online survey was carried out to analyze IM users' behaviors. The results imply that the degree distribution of IM users doesn't follow power law characters. Based on the data analysis, a new evolving model for IM user topology is proposed which contains two main principles: preferential attachment in local world and acquaintance recommending. There is a good fitness for the simulation results to the actual data.