[throwaway2037]

A better question to ask: Regulated futures markets haves existed in the US for over 100 years. Why haven't they added sports (or any other category that prediction markets cover)? The answer is simple: There is no legitimate economic need.

[mikeyouse]

Right. Futures markets exist to hedge some already present risk.. airlines can buy fuel futures to protect against the risk of fuel price rises, etc. Prediction markets create a new source of risk.