A couple of quotes I found of interest. First, on measuring social interaction:
"What's hard to measure, and what we're trying to measure," Mr. McKenzie continued, "is the impact of groupthink, of group mentality, and the tendency of what we might call the democratization of social interaction and how that changes this generation's relationship with almost everything they come in contact with."
Web analytics, as we know it, can only help with part of this equation. This is an area where properly applied AttentionTrust ideas might lend a hand.
Second quote - regarding advertising in non-traditional environments: