There have always been risks in marketing. Some things have changed. The grain surpluses of the late 1980's are gone. World demand has been strong and supplies have tightened up in recent years. One good crop year will no longer cure tight supplies.
Demand is strong, but users have become more comfortable in dealing with tight supplies.
This caused sharp price moves in last summer's corn market, when users scrambled to meet needs before the new crop became available. Tight supply markets are very sensitive to any changes in fundamentals. As the new crop harvest began, prices dropped quickly. It's easy to be wrong. They took advantage of what had been historically high prices only to see prices go much higher to record levels.