My sister sent me a great video on how our current monetary system works that I encourage all of you to see (watch all 5 parts).

It explains this question of how current and past financial crises are built into the system.  The reason is that nowadays money is backed by debt, e.g., every dollar banks create is backed by someone taking out loan from the bank, at interest (and to be more precise, every dolloar is only backed by a fraction of a loaned dollar, thanks to our fractional reserve system). The fact is that the system assumes in the future there will be more debt and therefore more money to pay off not only the loans but also the interest on them; it's basically assuming an ever-growing society, in terms of  productivity, economic activities, etc, that drives the need for more loans and thereby create the bigger money pool needed to fully back existing money pool (otherwise they are just paper) plus interest.

This assumption of an ever-growing society is not sustainable (because businesses do go bust) and can be downright dangerous, for the world to keep wanting to grow, depleting our natural resources on the way, and trying to achieve growth by perhaps taking excessive risks (like the mortgages and their packaged securities in this crisis). The central banks' (the Federal Reserves in the US) tinkering with the system by printing money without backing is not really solving the problem, and actually adds fuel to the fire by adding more debt to the citizens (inflation is really another form of tax) that assumes even bigger productivity (fingers crossed) in the future to repay it. 

This begs the question that perhaps we should change our out-dated monetary system to not back our money by debt, or make our money an interest-free instrument.