This picture comes from Reddit’s Just Rolled Into The Shop and shows what can happen to an economy brake pad that has minimal corrosion protection. The corrosion has worked its way between the backing plate and friction material. This has caused the friction material to delaminate from backing plate. At least 25 percent of the friction material is missing. This is a significant loss of braking power. The user who posted the picture said the driver brought the vehicle in because the pedal felt funny.