It's an allright idea.
What I'd rather is that you could set a point where the contacts can start and list, for example on a title bar, alligning it to the [ _ ] [ X ] buttons
Mozilla firefox [ Contact 1 ] [ Contact 2 ] [ Contact 3 ] [ Contact 4 ] [ _ ] [ X ]
to:
Mozilla firefox [ Contact 1 ] [ Contact 2 ] [ Contact 3 ] [ _ ] [ X ]
When Contact 4 goes offline
PS: Dont double post