TedtheLed makes a very good point about using the language and concept of betting in order to get people to quantify their surity of knowledge.
Turing this around, a 'futures market' provides a great tool for distilling and evaluating group knowledge available on a topic. If suddenly lots of people start buying a future that pays off if world leader XXX dies, then either they have discovered an unknown problem that the pentagon _should_ be looking at, or they are acting on a well known issue that everyone knows about and thus the future will only pay off a small profit (or none at all).
Also, while there is a certain amount of risk that individuals might try to 'force the market' by betting that a leader will die and then tring to kill them, what better way to discover who wants someone dead. Additionally, since in such a market the winners have to be balanced by the losers, anyone who wants to see someone dead will be balanced by people who have a monetary interest in keeping that person alive.
I believe that running this 'Terror Futures Market' is potentially a great intelligence gathering tool. I'd make the following requirements: 1) Terror futures should include 'betting' on American losses, as well as 'foreign' losses. Think of the intelligence boon if there were a sudden upsurge in foreign investment on a US terror attack.
Of course, since this is an intelligence gathering tool, and should be used to prevent the terror attacks, incentive should be built in to help stop the attacks. So there should be a larger payoff if the 'invested attack' is actually going forward, but then the attacker or the terrorist cell gets caught. This would put people who might have knowledge about an attack in the position of 'if I invest, then I could make some money. If I invest and then rat the bad guys out, I could make even more.' This could turn the 'futures terror market' into a 'forward reward' system.
-Jon