WhoKnows believes each user's privacy is of the utmost importance. Therefore, there are two levels of visibility to your contacts.
First, you control which contacts are visible or not. WhoKnows helps by automatically hiding any contacts that just have personal emails since WhoKnows is focused on professional relationships. You control which relationships are visible or not on the Relationships tab of the Edit Profile page.
Second, nobody can see your contacts until you choose to share them. You can select individual colleagues or people to share your contacts with in order to grow your own private referral network. If you like, you can choose to share your published contacts with your entire network as well. Your visibility is controlled on the Visibility tab of the Edit Profile page.