The flow analogy is central to our work in COSMIC, Mechanicity and related projects which argue that cities should be considered as first and foremost as flow systems, not as locational patterns. This is massive break with the past as it presumes that we cannot understand locations without knowing about flows. It blows up the problem dimensionally and it means that for every non trivial locational pattern, there are a countable infinity of flow patterns that can give rise to it. This is intrinsic to the derivation of spatial interaction models using entropy maximizing which is another feature of work in CASA and although this conundrum of interaction and location has been known for many years, only now is it being exploited. Social flows of course are the hardest to observe but social media may hold some clue. Here is a map of the tracing of single short text messages from Twitter taken from the London riots and plotted in Gephi, I guess,
The New York City startup SocialFlows is at the forefront of these developments although they are mainly concerned with optimising your tweets. As a side product, hey produced the map but of course this is what this kind of viral marketing is all about. Check them out.
There is a nice article by Mike Orcutt in todays Tech Review 22nd December 2012