Are you accessing the contacts over https? If not you will neeed to. Here are what google and yahoo say about it.
Reference url: https://developer.yahoo.com/social/contacts/
To safeguard user data and authenticate API calls, we are limiting all access to the Yahoo Contacts API to secure SSL connections only. No user data will be accessible over HTTP from this date onwards. Thus, your applications must use SSL connections when making requests to https://social.yahooapis.com or https://query.yahooapis.com to access Yahoo contacts/profile data.
Important: As of March 31, 2014, in order to increase security, the Contacts API began redirecting HTTP GET requests to HTTPS, and rejecting POST, PUT, and DELETE requests made with HTTP. If your application uses the HTTP protocol, please switch to HTTPS.