Vice President Cheney has promised that Iran will not get nuclear weapons.
If we had a very liquid current events prediction market then the U.S. government could bet, say, $20 billion that over the next 10 years Iran will not explode an atomic weapon.
Such a bet would make it far more credible that the U.S. would stop Iran from going nuclear. It might thus discourage Iran from trying to acquire atomic weapons.
The disadvantage of the bet, of course, would be that those on the other side of the U.S. on the bet would have a large incentive to help Iran get atomic weapons.