prediction markets seldom work as people say what they would like to do rather than what they would actually do.
an example, there was an experimet done a few years back.. cant find a link.. about day traders having better trading abilities before they were told they are actually dealing in real money transactions.
Yes! i do understand that , people predict and the rumour alone cause a rucus and a rise , if they actually do it , the value stays and it again falls.