There are 2 different Ad types that are available for posters:
Public Ads - Regular ads where all the information can be seen by all users and messages are seen by everyone. Unless the admin overrides it and messages can be seen only by logged in users.
Private Ads - The address is hidden to users and only the Country and City is viewable. Messages can only be seen by the owner and the user that sent/received the message. The Google Map is also hidden.