Maciej Ceglowski's "The Social Graph is Neither" is a scathing, spot-on critique of the deceptive and seductive simplicity of "social graphs" which purport to represent human interaction and relations through mathematical modelling. As with many "semantic web" projects, social networks can only achieve any kind of usable scale and coherence by simplifying the relationships they model to the point of triviality.
One big sticking point is privacy. Do I really want to find out that my pastor and I share the same dominatrix? If not, then who is going to be in charge of maintaining all the access control lists for every node and edge so that some information is not shared? You can either have a decentralized, communally owned social graph (like Fitzpatrick envisioned) or good privacy controls, but not the two together.
There's another fundamental problem in that a graph is a static thing, with no concept of time. Real life relationships are a shared history, but in the social graph they're just a single connection. My friend from ten years ago has the same relationship to me as the friend I dined with yesterday. You're left with forcing people (or their software) to maintain lists like 'Recent Contacts' because there is no place in the model to fit this information.
"No problem," says Poindexter. "We'll add a time series of state transitions and exponentially decaying edge weights, model group dynamics as directional flows, and pass a context object in with each query..." and around we go. p> This obsession with modeling has led us into a social version of the Uncanny Valley, that weird phenomenon from computer graphics where the more faithfully you try to represent something human, the creepier it becomes. As the model becomes more expressive, we really start to notice the places where it fails. p> Personally, I think finding an adequate data model for the totality of interpersonal connections is an AI-hard problem. But even if you disagree, it's clear that a plain old graph is not going to cut it.
(Image: Map of top 50 UK PR twitter people and their followers, a Creative Commons Attribution Share-Alike (2.0) image from porternovelli's photostream)