One of the major factors UL takes into consideration is the flammability characteristics of the insulation material.If a cord shorts out do to overload,or a pet walking by the cord moving it causing insulation failure.I would guess everyone here moves their cords to clean when they choose.The extension cord mentioned above must have had flame retardant insulation to keep it from bursting into flames taking everything with it.I myself like to see the UL listed marking on my cords.For digital audio, shielded power cords help keep out stray noise generated by radio stations,and possibly the power supply on one of your components.This is just my choice.
