There may be other dynamics, in addition to the imbalance of debt and real wealth, that produce "boom and bust" cycles in an economy.  

I recall that as an undergrad, years and years ago, I had a prof who reported (with a chuckle, as in "could anything be more ridiculous?") that "there is even some evidence that stock market ups and downs correspond to sunspot activity."  Hmm...  Sunspots affect solar output, which affects agriculture, which is still one of the primary ways that valuable low entropy is brought into an economy (despite the fact that there has been an historical decline in the percentage of the workforce engaged in it.  Look for that trend to be reversed as we come off peak oil and are forced to practice sustainable agriculture.)  

Interesting analogue:  

unless the predators precisely manage their fertility and their hunting quite carefully there will be boom-bust cycles, and even a stable system will start oscillating in response to an external shock.

 

Imagine if the predator population (representing claims on future population of prey) can grow exponentially, because they are (like debt) incorporeal abstractions.  The boom and bust cycles could then easily become large enough in oscillation to threaten not only the dynamic equilibrium implied by the sinusoidal chart, but the continuation of the system as a whole, through the removal of the prey species entirely.

Industrial society is not sustainable. Unsustainable systems change--or disappear.