The short-lived commodity inflation was caused by speculators who had access to very inexpensive money - courtesy of the Federal Reserve. It was predictable (lots was written about it), but short-lived because the deflating asset bubble, caused by extraordinary debt burden, was inevitable. Lots was written about this, before it happened. It was our incompetent government that kept feeding greed with loose money that perpetuated the problem. It appears that commodities are bottoming out for the time being, because of the extraordinary measures, taken by governments all around the world, to prevent deflation.
Going forward, it is highly unlikely that we will experience anything similar to the Great Depression, where banks were failing because of runs on banks, and government was putting a tourniquet on the money supply. What will happen - since this is all unprecedented, is anyone's guess. But I am thinking that the government capital spending will swell certain sectors of our economy, that will somewhat offset weak consumer spending. But we need to turn around lots of industries in the process and make them whole again - including heavy manufacturing and auto.
It will take time, and is doable. I am thinking that there will be a substantial rebound, once it is clear that unemployment will not go over 10%, but then equities will reach a relatively fair market value and bump around there for several years, as the economy repairs itself.