Gambling on the stock market index.... A newbie question.

[BlueBear]

Hi,

Newbie question here.

I have seen several on-line sports exchange trading sites that offer contracts based on the stock market index. (eg. Dow Jones Industrial Index). For example, a contract could be that the DJIA gains 25 points over one day.

How do market index futures and options differ from these sort of contracts sold in betting exchanges? I understand the the index futures is a well established derivatives market with huge comporations using it for risk management (hedging) purposes and these index future markets cater to large corporations... But in what way are the index futures and these "betting exchanges" different?