Wishmii

WishMii is a social network based on groups not people.
You can create all the group and events you want, both personal and corporative.
Groups can be public or private.
Public groups can be found using the search engine and everybody can join them.
Private groups cannot be found using the search engine and users only can join them by invitation.
Group admins can create new events, block new users subscription, block members activity and delete messages.
You can chat with other users and block the ones you do not want to.
And above everything: Free, anonymous and ad free