The AOL Instant Messenger group took the deepest cut so far. A former AOL employee said the group was "eviscerated and now only consists of support staff."
This is not entirely unexpected due to competition from Skype, Facebook chat, Google chat; I could go on. Kinda sad considering that the first thing I did with my first (solely operated) computer was create an AIM screenname that I used all the way through college. That's been completely replaced with Skype for me.