Ric is right about the relevance of growth literature to this discussion.  
Any country, rich or poor, where the marginal product of capital is below  
the sum of the rate of depreciation and the population growth rate has  
over-accumulated capital and is "dynamically inefficient". Diamond's 1965  
AER article shows that this is possible in a competitive economy under  
laissez-faire--no "frictions" other than finite lives are necesssary. A  
dynamically inefficient economy can be Pareto-improved by drawing off  
"productive saving" into unproductive forms--fiat money, perpetually  
rolled-over government debt, pay-as-you-go social security--reducing the  
capital stock and raising steady-state consumption. This possibility is  
the long-run analogue of the Keynesian "paradox of thrift": the economy  
really is over-saving, although it is not at all an aggregate demand  
problem--it's a missing markets problem due to the "friction" of finite  
lives (in the long run we're all dead and the unborn aren't around to  
trade today!). The remedies sound pretty Keynesian, too.