Permissions on items look more complicated than they really are. Once you add a one or more members to a group, those members will then have access to any items (blogs, images, etc) where that particular group has been given Read, Reference, Respond or Revise. However, if you change that group's permission on an item to None (private), then all members of that group will be denied access to the item. This same technique applies to any groups you create.

The last group, Everyone, isn't...