I have dragged several contacts to different groups in the contact list and every time I've got a window prompting me to send an authorization message. It seems strange that simple reordering of contacts in my list requires the authorization procedure for contacts already authorized. Moreover, I have pressed cancel for two contacts, quit Adium (1.0.2), restarted into MacOS 9.2.2 (I had to), and launched ICQ 3.4 there. Guess what happened! These two contacts merely disappeared (together with their chat history!!!). I restarted into MacOSX (10.4.9), launched Adium, and found that these contacts disappeared here too (though, luckily, the chat transcripts are still in place).
Maybe I missed something important from preferences, but if no, then this (mis)behavior is unreasonable and annoying (authorization requests) and potentially dangerous (loss of chat transcripts in other ICQ clients).