There is general consensus that critical mass at inception ensures the sustained success of online communities. However, no clear understanding of what constitutes such a 'critical mass ' exists and too few quantitative studies have been conducted into the relationship between initial online community interaction and its longer term success to draw any conclusions. In this paper we start to address this gap through a large-scale study of the relationship between IRC chat channel survival and initial chat channel community interactions. A sample 282 chat channel births was used for survival analysis which explored the relationship between the overall user activity in each channel at its inception and the channel's life expectancy. Significant relationships were observed between online community lifespan and critical mass measures: 1) message volume, 2) user population heterogeneity and 3) production functions. The results lend support to the Critical Mass Theory of collective action.

Prior work has demonstrated that the impact of individual information-processing limits can be observed in dynamics of mass interaction in asynchronous collaborative systems (Usenet newsgroups and email lists). Here we present the first evidence of such impacts on synchronous social interaction environments through the analysis of an Internet Relay Chat network. We highlight how shared public discourse in chat channels appears to be limited to 40 posters in any 20 minute interval, even as the number of channel users increases well into the hundreds. We discuss our findings in terms of understanding the relationship between online community space types and the user interaction dynamics they support.