Messaging module
When selecting a recipient of a messaging module message, you can conveniently switch to the Friends tab and select one of your friends just by clicking their user name.
Fields visibility
Users can set the visibility of some fields on their public profile to Display to friends, which makes the field visible only to their friends. For more information on this feature, please refer to Development -> Membership, security and permissions -> Custom fields visibility.
Page url: http://devnet.kentico.com/docs/5_5r2/devguide/index.html?friends_example_of_use.htm