Real money would definitely be preferable but I'm pretty sure that idea is a non-starter. You run into gambling regulations with prediction markets and it appears that it is currently pretty much impossible to run any kind of gambling operation in a way that is reasonably accessible to anyone in the US. US credit card companies generally aren't allowed to process payments for online gambling sites. Even outside the US there is a minefield of regulation to navigate.

InTrade suffers from this - even though I live in Canada rather than the US I haven't been able to fund my account with a credit card.