Quite remarkably, the mean rates of contact in each layer are extremely close, especially for the Facebook data sets, to those found in (and, indeed, used to define: Dunbar and Spoors, 1995) the different layers in egocentric offline personal social networks (Sutcliffe et al., 2012). This suggests that the online environments may be mapping quite closely onto everyday offline networks, or that individuals who inhabit online environments on a regular basis begin to include individuals that they have met online into their general personal social network, treating the different modes of communication as essentially the same. This, of course, has important implications for both the design and promotion of online social environments. However, our present concern is with the sociological similarities between online and offline environments, as implied by these data.