Doing this kind of show isn't exactly a win-win: I would guess the volume of crackpot mail I receive could go up by an order of magnitude :-(
Semi-classical wormholes and time machines are unstable
Abstract: We show that Lorentzian (traversable) wormholes and time machines with semi-classical spacetimes are unstable due to their violation of the null energy condition (NEC). Semi-classicality of the energy-momentum tensor in a given quantum state (required for semi-classicality of the spacetime) implies localization of its wavefunction in phase space, leading to evolution according to the classical equations of motion. Previous results related to violation of the NEC then require that the configuration is unstable to small perturbations.
Here are some slides on the subject. Click for larger version. For more background on why it is difficult to construct effective field theories which lead to (stable) violation of the null energy condition (NEC), see Phys. Rev. D 74, 063518 (2006).