I learned about https://en.wikipedia.org/wiki/Assassination_market in the early 2010s. It wasn't phrased like a prediction market focusing on when a person would die, but more like a bounty. If the bounty/pot got big enough, eventually it would be worth it for someone to do it.
Even thinking/writing about this now, it still makes obvious sense and I'm surprised it hasn't been seriously made yet with crypto: if there's a pot of billions, contributed to by millions, the incentive becomes not just about the money, but the adoration, protection and power that would come with doing so many people a favour.
It seems to me you underestimate the challenges of getting the money from such crypto scheme. A murderer would have to prove to the pot owner that they are, in fact, the real murderer and not someone pretending to be one to get the money. However, there’d be another actor trying to prove who the murderer is - the police. So, you’d practically have to dox yourself in order to get the money, or be able to have such a strong privacy system that a state actor cannot break it and identify you from your communications with the pot owner (lol). If you have such a strong cyber security system, you’re probably better off just selling it for $$$$$$ than muurdering randos.
But these problems would likely be self-resolving in most cases as the crypto pot owner would simply rug-pull everyone.
I think all the big targets for this kind of thing have the legal or government muscle to get in your way? Millions of people usually don't agree on someone dying unless they're powerful.
Even thinking/writing about this now, it still makes obvious sense and I'm surprised it hasn't been seriously made yet with crypto: if there's a pot of billions, contributed to by millions, the incentive becomes not just about the money, but the adoration, protection and power that would come with doing so many people a favour.