I discuss thermal effects on the potential between static fundamental charges in a QCD plasma. I focus, in particular, on the emergence of an imaginary part at high temperature. This provides a non-zero width even for small, deeply bound quarkonium states. I show how the imaginary part is computed via resummed (real-time) perturbation theory at weak coupling; and via the gauge-gravity correspondence at large t'Hooft coupling. I briefly mention how this could be relevant for heavy-ion collisions at RHIC/LHC, such as suppression of R_AA(Υ -> e+e-), or quarkonium coalescence.