When you click to invite other people to the site there is a check box for automatically creating their membership and adding them to the group. I feel that that should be left entirely up the people who are being invited and not an option at all for the person doing the inviting.
Theoretically there are people who will be invited to the site who might not want their email address associated with a profile there.
Other than that I think it has lots of potential. I especially like the idea of the chat feature.