Obviously this is a crazy idea and noone should do it, but if a prediction market let you bet on what day someone would die, someone could insider trade the market by placing a big bet on the day they go and assassinate them. People could place bets on random days for people they don’t like to push up the value of the winning bets.
That’s how it’s already done, afaik. But cheers for coming up with the idea independently (if you didn’t read it in one of the discussions about Polymarket, of course).