ICQ is so lame that the contact list is stored on your local computer and isn’t stored on the ICQ server. I want to use the same ICQ account at home and at work, and I want to share the contact list between them. The solution? Copy the contact list and manually send it to the other computer. Weak. (By the way, Yahoo Messenger has this figured out already. Your contact list is stored on the server.)
This page keeps track of the ICQ protocol. It seems to be getting more and more difficult to reverse engineer.