Are prediction markets not actually useful? No, it is the reality who is wrong.

Also I want to rant once again about the stupid way these people evade the insider trading problem, because there's a particular failure at play that I keep finding expressed in new and interesting ways.

So the argument goes that while insider trading may be bad for a financial market it actually just allows insiders to add their information to increase the predictive power of the market. Which would be true enough if we assume nothing else changes, but the same would also be true for price discovery in a normal asset market. Clearly we're missing something.

So why is it insider trading bad? Because it turns people without insider info into the dumb money you can take advantage of. And people, very reasonably, aren't going to participate in a system where their main role is being taken advantage of. Their departure means that the insiders don't have access to a pool of dumb money to take so they stop interacting with the system, and the market itself breaks down.

Now if you assume that the majority of people are "NPCs" or aren't very "agentic" or whatever then they're not going to act in systemically meaningful ways no matter how obvious the incentives to do so. You could also cast it as a version of the libertarian-as-housecat notion that markets simply exist as a natural system, rather than being pieces of economic infrastructure that require a lot of management and work to keep functioning at all, even before we get to the question of whether they operate to the public's benefit. So many of the problems with these ideologies spring from this belief that only some people actually matter in a systemic sense by dictating rules and Building Things and being big men, rather than systems being constantly created and shaped by all the people who interact with them through those interactions.