one extremely dim? My thoughts were either they got into an accident and went to some cheap junk store that repaired it poorly for very little money, so they took no time to aim the headlights after putting them back in. Or, people fiddle around with their lights too much when replacing their bulbs and somehow severely knock them out of alignment? There's a third option I dismiss mostly because it seems less reasonable is that some cars just get out of alignment after so many potholes and bumpy roads for years. Does anyone know the cause for sure or have their own theory?