Freakonomics points to a study which researched why the Chinese save so much. Of all the more obvious answers that subsequent commenters on the post came up with (like economic prosperity, social values of thrift etc) they link it it to China's one child policy;
China’s “one child” policy, which created a huge surplus of men in the country, has driven up the cost of getting married, as more and more men compete for fewer and fewer women. To keep up, families with sons have been holding off on spending to save up wealth that boosts their children’s marriage prospects.This leads one to wonder why there are fewer women in China in the first place, and research studies have attributed this to hepatitis B (but later dispoved by the same author), sex relative wage rates and sex selective abortion as a practice.
Also as it turns out, or as i just found out, Ben Bernanke has been saying the increasing rates of saving in other countries caused the US housing collapse. He claims that increasing savings in other nations along with liberalization and the removal of capital flow barriers created a disconnect between US long term lending rates and Fed Monetary policy.
A credible argument, but it still doesn't explain how they could just let it happen, and the myriad other inconsistencies in the actions of the fed over the few years leading to the crisis.
From China's savings to Missing women to the Global Financial crisis; This is why i like Freakonomics.