This would arguably be much more severe -- and quite likely already happening -- than the whole "congress trading stocks" thing because most of those (besides the sports ones) tie very directly to government actions in a way that the economy or a large company in generally doesn't as predictably.
Maybe this is fine until it incentivizes easily-achieved but adverse actions that would greatly harm the public.
For a silly example, I would imagine the streaker from this year’s Super Bowl is either (a) a complete idiot, or (b) put a significant amount of money on a “prediction market” of there being a streaker at the Super Bowl - more than enough to cover his ticket, legal, and medical costs.
This would arguably be much more severe -- and quite likely already happening -- than the whole "congress trading stocks" thing because most of those (besides the sports ones) tie very directly to government actions in a way that the economy or a large company in generally doesn't as predictably.