There’s no rubric, but I’m assuming that this is a form of network graph — where each node may itself become the source of new edges.
What’s interesting, if that’s the case, is how only a few shares lead to huge bursty cascades of sharing. I’ve seen this before on much smaller data sets:
There’s a potentially useful paper, The Dynamics of Viral Marketing, (Leskovec et al., 2007) that addresses this phenomenon. I’d be grateful for links to other papers — or your thoughts.
Thanks to somerandomnerd for the link.