Are Markets At The Edge Of The Cliff?

Sydney Morning Herald, via The Big Picture:

So this is a global sell-down, and a big one. But so far it is still driven by uncertainty rather than a consensus view that the battle to pull the world out of the hole it dug for itself in the 2007-09 financial crisis has been lost. From here the market could rally sharply or descend into a genuine crash that tests the 2009 global crisis lows, depending on the verdict.
There's a lot to worry about. This week it includes Italy's sovereign debt downgrade, debt ratings cuts for three big US commercial banks, Bank of America, Wells Fargo and Citigroup, reduced IMF global economic growth estimates, signs of a slowdown in the world's last growth engine, China, and comments from the US Federal Reserve down that global growth has slowed alarmingly.

The Fed's decision this week to sell $400 billion of short-term debt and use the money to buy long-term debt is a plus, as is the G20's promise to produce a crisis prevention blueprint by early November at the latest.

The commodity declines are troubling me the most.  Will grain markets collapse before harvest is complete?  Should I be locking in prices for 2012 crops?  I am guessing that prices will drop dramatically if the Eurozone falls apart, but for how long?  The price runup has been extremely beneficial for farmers, but it isn't going to last forever, and the collapse will be much more painful than the climb was helpful.