Well I think part of the reason people at so depressed about old friends disappearing is because they probably just had a different mentality then. Everybody had a goal to strive for, like clearing Ciar for instance. We were all weak and shared similiar goals do it was really easy to make friends, and by that I mean GOOD friends. Now that everyone can plow through everything with sheer damage there isn't that common goal and its a bit harder to make lasting friends.
Like others have said, if they dont log on for a while. It's better to just move on and just find new friends.
That's just my take on it though.