Independently of its precise definition, electronegativity is a powerful concept for quickly predicting the direction of charge transfer and bond polarity. But even so, we know that trends in this atomic property can disagree with a range of observables, such as trends in bond energies, reactivity or stability. For example, the dipole moments in molecules such as CO, CS and BF are inverted relative to expectations from simple electronegativity arguments (these dipole moments can be explained in other ways). We believe this work constitutes an important step towards better understanding the occasional practical shortcomings of electronegativity.