I think one could argue that Will Smith (at least) HAS added something to the community. I suspect that a number of people here wouldn't have been here were it not for The Pursuit of Happyness. In fact, I kind of suspect it was only because of the extra attention the cube was getting at the time that I decided to pick speedcubing up back when I started. So at the very least, it seems likely that Will Smith helped add me to the community. I suspect there are many others.
And as much as it might disturb some other people here, I suspect that if we look a year from now, there will probably be quite a few other people added to our community because of the extra attention Justin Bieber brought. I seriously doubt it will be of the same scale as what Will Smith did for cubing, but it will probably have at least some effect.
They qualify as notable cubers, in my opinion.