I read Fred Wilson‘s post on Explicit vs Implicit Groups tonight. It struck me that the right model for Google Plus (and any group based social network) is the concept of “aged groups”. So I can toss anyone into a group but over time a lack of interaction or engagement “ages” them out of the group. So groups remain small and focussed on the active members. The asynchronous nature of Google+ groups is ideally suited to this model and could be an option for users to set on their accounts.
With aged groups I’d be much more likely to allow Google+ to parse my address book and add members based on groups I already have setup or even suggest groups based on email conversations I’ve had in the past.
The key issue is for the groups to reflect the dynamic nature of relationships. I work in a company and then I leave, guess what? most of those relationships die within a year or so. I don’t want those (now) strangers still shot through my Facebook and Google+ account.