How can we make sure accounts are only used by the designated user?

The Terms and Conditions of Use agreed to by users befpre they use their accounts for the first time prohibit sharing a personal Athens account with anyone else. Most content providers do not consider it necessary to verify the calling IP address for personal accounts; however, this may not always be the case for future services. In such cases, further restrictions can be placed on accounts by preventing them from being used outside certain designated IP addresses.