My friend Auren periodically pens insightful posts about topics on his mind.  He recently shared his thoughts on social shopping.  To summarize:

Social psychology
has shown that people tend to develop relationships with those that have
similar interests to them, transcending demographics and psychographics. And those that have a strong relationship
with each other have the capacity to influence each others’ behavior.

Marketers traditionally have put consumers into various
buckets in order to compartmentalize and therefore easily learn and make
assumptions about them. These marketers
lack the Holy Grail social-graphic information: friend connections and
relationship information amongst their consumers. 

I agree with Auren in that the power of the social graph as it related to shopping behavior is extremely tempting.  In fact, I suspect that Beacon was the "wow" element in Facebook’s $15b valuation round.  However, I also think the trick to successfully putting social graph to e-commerce use is more complex than it first appears.

Auren lists those who have access to various types of social graph information:  telecom providers,
social networks, webmail and IM clients, and search aggregators. It’s true that all of these companies possess a slice of the social graph information, but each slice represents varying contexts.  Connections represented in one’s business email account will vary vastly from those in her personal one.  The problem is you can’t really make assumptions on which is more relevant for commercial behaviour.  Some will related better to their business contacts, others to friends, yet others to family.  An additional layer of complexity is in identifying the context of the email account.

Effective marketing using social graph data is probably closer to traditional targeted marketing than a truly AI-driven pinpoint attempt like beacon.  It’s a very fine line where these presumptive attempts start feeling creepy (not unlike the "Uncanny Valley" phenomenon in robots).  If a marketer starts assuming that my ex-girlfriend is my mother because I called her a few times on mother’s day, it’s not effective marketing.  In fact, Auren had a funny post the next day about how Evite thought he was a woman.

I do believe the social graph will continue to be a tremendously useful data set for marketers.  But, I think it will remain more an art and less a science.