Can heavy quarkonia be used as thermometers in heavy-ion collisions?

Heavy quarkonia have long been proposed as probes of deconfinement in heavy-ion collisions, and more recently, they were put forward as thermometers of the created matter. I examine this claim in the view of our knowledge on the dynamics of the medium, and argue that quarkonia are far from constituting such a tool. Eventually, I present some options for describing heavy quark-antiquark pairs in a dynamically evolving environment.