Think of these new groups as listservs. A way to stay in touch with your group or team.

Listservs + Yammer actually with the group chat feature.

As I wrote on the wall, I think it might work better for things local (connecting with HN'ers in your area). But I am also thinking that this could actually be a place where I might go to ask for quick advice, stuff that's too small to make a post in here about.