We review the experimental evidence suggests that substantial fractions of typical YBa2Cu307 samples are non-superconducting; that the non-superconducting inclusions are of dimensions of a lattice parameter; that the non-superconducting inclusions are associated with Cu^2+ magnetic moments; and that the linear term in the specific heat is not an ”intrinsic” property but is associated with the presence of these Cu^2+ magnetic moments and impurity phases. A preliminary result on the effect of heat treatment on the volume fraction of superconductivity is also presented.