I have noticed that the number of the friends, on my profile page, has recently decreased by a few. That in itself is fine. I understand that people's MiceChatting habits change. It would be nice if we could get a notification that a friend has left, in the same way that we do when they become our friend.
Sometimes, I figure it out, and then sometimes later, when I think about sending someone a note, I realize they aren't there any more.