If you are a "radical roleplayer", keep it empty, and hide the window.
But do not attempt to decide over the opinion of other people who are not such pure roleplayers, and prefer to know the presence of other players. It is everyone's personal opinion to use this feature, or not.
A feature to let a player decide wether he may or may not be added to anyone's buddy list, may be an alternative feature we could talk about - similar to the "invisible" mode of a forum member. Maybe even a feature to decide if you want to be able to receive tells, similar to the feature to decide wether to exchange Personal Messages in a board.