What 'unexpected' everyone is talking about? Everyone has been pointing at US imbalances like low saving rate leading to dangerous dependence on consumption for

What 'unexpected' everyone is talking about? Everyone has been pointing at US imbalances like low saving rate leading to dangerous dependence on consumption for growth (and consumers in turn depending on low rates to borrow) for 5 years at least. What's unexpected is that it took so long to unravel.