* Personal work as circles do currently - i.e. its your way of organising your own contacts; no one else knows what personal circles you have or who's in them (including the members).
* Group is a shared contact list - any member of that group has a copy of it, and has permissions to maintain it as if they'd created it. This would be useful if I wanted a group of people in my sport team / band, since when one of the band already in the group adds someone to this group, everyone in the band can then talk to them; and it's not up to me as the creator to do all the admin.
* Owned Group - essentially the same as Group, but with additional security / more like FB's groups. I specify who's in the group and what access they have - i.e. if they're just a member, or if they can also administrate the group. This is more useful for application fan pages, where you want a mailing list of people to contact, but only want a few of the people in the group to be able to add / approve new members. With this model, it would be OK to have an option for non members to request access; then be added once approved.
What do you guys think?
JB