A colleague of mine at work recently graduated, and was telling me about his thesis, which touched on the banking crisis of a couple of years ago. Apparently a credible explanation of this crisis, among economists, and the one my colleague was taught, was that the problems originated with the extension of the right of home ownership to low wage workers. The whole thing was presented as if it was a transgression against nature for workers to own property, which inevitably called down vengeance from heaven.
The crisis certainly followed on from a great period for the issuing of bad mortgages, but both these circumstances were results of the maturation of the underlying asset market. Without bad mortgages the market would have levelled off five or ten years sooner, money would have become tighter, market interest rates would have risen, banks would have become insolvent, (as they periodically do).
tightening of money follows from the maturation of asset markets