Athens.
The second and last day of WebSci '09 starts with a session on social networking, although the first paper in this session, by Yorgos Amanatidis, has the somewhat technical title "Kernels for Complex Networks" - we'll see what that's all about... Visual network graph models, apparently, for graphs which represent relational data in an abstract way. Such graophs can be used in the analysis, simulation, and prediction of network topologies, focussing especially on aspects like scaling, clustering, and node centrality.
What can be observed in real networks is the degree distribution: as the Web grows, the average degree is constant, but there is huge variance and no concentration around the average; indeed, we see the small world phenomenon which produces networks with small diameter and strong clustering tendencies (the friend of my friend is likely also to be my friend). Kleinberg, for example, modelled the fact that in small world networks there are not only short paths between nodes, but that these nodes can find such paths effectively using local information.