  Massless black holes can be understood as bound states of a (positive mass)
extreme a=\sqrt{3} black hole and a singular object with opposite (i.e.
negative) mass with vanishing ADM (total) mass but non-vanishing gravitational
field. Supersymmetric balance of forces is crucial for the existence of this
kind of bound states and explains why the system does not move at the speed of
light. We also explain how supersymmetry allows for negative mass as long as it
is never isolated but in bound states of total non-negative mass.
