One of the best aspects about running groups online in a contained environment should be the ability to diagnose the groups using the ideas of social network analysis. Identifying who is central to the conversation, who is quiet but respected or who is a connector is fairly basic as long as you know who communicates with who and in what order. Google Groups unfortunately doesn't allow any of this basic analysis. The only information shared is the number of posts by each individual.
The social networking information is a fairly valuable dataset. I would be surprised if Google isn't analyzing this information on the backend and adding to its great store of data on the way we interact.