"X was last online Y days ago"

If we had this feature in the friends' list, it would tremendously help with managing it. As of now, I have so many friends added, but I'm afraid of removing any of them because I may or may not know them well enough to regret removing them.

People come and go, and it'd be nice to have a feature to be able to tell when someone was last online so we can see who's inactive or not.