I've certainly seen power quality degraded over the past 20 years or so. Before the days of switching power supplies (like VFDs, electronic ballasts, computer equipment and the like) the waveform of just about any service was smooth and linear. These days, it's anything but smooth.
This distorted waveform will have almost no effect on anything resistive (like an incandescent light, or a heater), but an inductive load (like a motor or transformer) will see the sideways shift that occurs in the waveform as a reversal of voltage. It will induce power back into the line, only have it shoved right back, because the wave wasn't done rising or falling.
This causes additional heating of the windings and core. Not only is this bad for the inductive devices, but there is only one place this extra heat comes from. The incoming power line!
I really have to wonder what effect all these energy saving devices have on the national power grid as a whole.