Suppose I own ten rookie baseball cards of Cal Ripken, who is eligible for the Hall of Fame in 2007, and whose card trades for $60. We do not know if he will be elected; it seems a shoo-in, but things can happen that might tarnish his reputation between now and then (remember Pete Rose). Suppose I could guarantee now that I could sell the card for $70 next September to someone, and than that card would be worth probably $75 after election to the HOF. Do I sell now at $60, in September at $70, or January '07 for $75? What if there was a futures market that lets me guarantee?

Arnold Kling makes the same point about oil futures: The market is saying right now, hoard the stuff. The near contract (delivery of oil for June, is $72.45, $75.20 for October. If storage for six months is less than $3/barrel, wouldn't I save the oil to sell later? And why would I save? James Hamilton ticks off Nigeria, Iran, Iraq, Saudi Arabia, Venezuela, Russia, ...

The baseball analogy, by the way, is apt.