This is my opinion and could be VERY wrong but:

There is a lot of overlooking the primary reason for the runup in grains, fund buying.  A huge influx of dollars that normally wasn't there.  What happens when these dollars jump back to Wall Street stocks, leaving commodities to be actually at the wims of supply and demand.  My guess is a tremendous downturn in the markets.  The "hot air" of ethanol taking all the grain and forecasts of shortages made the commodities attractive to dollars normally not seen in the grain markets.  Results, run up in grain prices.  Not much money left to be made on the high side, soooo, time to take the profits and run.  Very likely will have ethanol still going and grains falling sharply in the not too distance future.

Hey, but then maybe not, as I am not a marketing brain, just haven't completed training for my marketing ID 10 T card.