In this talk we analyse a gedankenexperiment, which involves quantum superpositions of charged and/or massive bodies. In the electromagnetic case, we show that the quantization of electromagnetic radiation and vacuum fluctuations of the electromagnetic field both are essential for avoiding apparent paradoxes with causality and complementarity. We then analyze the gravitational version of this gedankenexperiment and show that it is in complete parallel with the electromagnetic case provided that gravitational radiation is quantized and that vacuum fluctuations limit the localization of a particle to no better than a Planck length. This provides support for the view that (linearized) gravity should have a quantum field description, a relevant result in view of the growing interest in proposals for table-top experiments probing gravity-induce entanglement.