I don't use AIM, myself, but I remember being annoyed by the commercials the few times I did have to use it on a friend's computer or whatnot. I just got this workaround in an email, if you want to silence those ads:
1) Go to the AIM95 directory in your program files
2) Delete advert.ocm
3) Make a copy of admin.ocm and rename it advert.ocm
Just in case anyone finds it useful.