Grim

I suspect the reason for springs failing is due to the fact that they are made in smaller diameters for packaging reasons. It could however be due to the use of dirty chinese / indian steel, which contains a lot of impurities such as slag and oxides. The impurities cause a locally high region of stress, which can set off fatigue cracking. I'm a metallurgist by trade, but i haven't had the opportunity to examine a broken spring to see for sure.