The October Scientific American argues that black stars more dense than neutron stars may form instead of black holes. Black holes are predicted by classical general relativity but do not take properly take into account quantum mechanics. A quantum effect called vacuum polarization may grow large enough to stop a hole forming and create a "black star" instead. Such a star would not have an event horizon but any energy emitted would be shifted far to the red and not show as visible light. A major problem with black holes is the loss of information that would occur violating a fundamental feature of quantum mechanics called unitarity. I have always been skeptical of singularities since in every other area of physics singularities mean a failure of the math or theory or both. When the theory predicts such things as infinite energy (the ultraviolet catastrophe) or singularities it usually means the theory needs to be modified.