This was my experience trying out "traditional betting" for the first time with Betfair last Worldcup, and some other platform I tried out before as well. Not sure what Kalshi/others are doing that is so different?
So, not all that different, but marginally less exploitative. I've never looked at Polymarket but Kalshi and PredictIt slid steadily from things of at least plausible real economic value (a market where it was conceivable [if unlikely] someone would be hedging their insurance contract or something) into total nonsense with no non-gambling function like whether someone would tweet a certain word.
I think prediction markets could serve a similar to a futures markets and have a functional purpose in the economy. It could be useful to generate real time estimates of the probability of some events that no one can control and have real economic consequences, like a hurricane. But evidently that's not where the money is.
But doesn't Polymarket et al own their own platforms, just like Betfair owns their platform? There is no P2P going on, even if some markets seem to advertise themselves as such so again, seems like the same just minus gambling regulations?
https://docs.polymarket.com/concepts/prices-orderbook
https://help.kalshi.com/en/articles/13823828-the-orderbook
Tl;Dr there's an order book with prices set by supply and demand. So you're at the whims of the market rather than the whims of someone who is your broker, exchange, clearinghouse, and taking the other side of your trade. I don't know much about Polymarket but iirc Kalshi is only your broker and exchange, so dealing with them is materially less risky in my mind.
Even though nobody can control them, some people can predict them better than others. (Meteorologists with good models and supercomputers, etc.) In general it's impossible to prevent the appearance of insider trading in prediction markets, and it's also impossible -- unless you massively restrict what people can bet on -- to prevent people from doing things for bets to resolve in their favor, which turns those "markets" into "bounties." (The same guys who theorized prediction markets were the ones who theorized assassination markets.)
They're fundamentally broken and the fact that they're allowed is a sign and symptom of a dysfunctional society.
In a broader context this may contribute to income inequality and regulatory capture, it can have negative externalities. But it isn't on it's face a problem. And the alleged positive externalities (realtime forecasts and a liquid market for hedging) are driven by such skilled traders.
Not all prediction markets are equally easy to manipulate. The bar was supposed to be (according to my hazy recollection) that a market had to be run in collaboration with an outside authority who, along with delivering a verdict that was already part of their normal duties, would help you exclude insiders from the market. That's a defensible position (not morally, tactically).
But "will so and so tweet about such and such" is a total joke. That's indefensible. That I do think that should never have been allowed or should be regulated as gambling. If there's no conceivable natural hedger, it isn't a real financial market and doesn't have a function (or the function is gambling, whichever).
Don't get me wrong, I think this turned into an end run around gambling regulations (that's certainly what happened with PredictIt), but I don't think that was always inevitable or will necessarily always be the case. That's a strong attractor for sure but it was pushed that way by the COVID era meme stock frenzy, the deregulation of online gambling, and ultimately competitive pressure from the sketchier markets. Once those forces were aligned it was inevitable, but it's possible that in 10 years there will have been a crackdown and tightening down of regulation and things will be very different. I'm not that optimistic, but it's a real possibility.
There are two ways to view a market (prediction or stock): as socially accepted gambling for posh elites (and now every wannabe rich), and as a prediction engine that refines people's opinions, beliefs and information into a most accurate estimate possible.
If you take the first view, insider trading is dysfunctional and unfair. If you take the second view, insider trading is the entire point, it's how you get strong signal into the system.
Prediction markets were conceptualized by people taking the second view.
(It's why I wrote about two perspectives - preferring outsiders to insiders only makes sense if the goal is to create a gambling venue.)
For large/complex enough bets, you won't have a single group of people who know how things truly are - you'll have multiple groups of people who each have (or believe they have) a critical piece of the puzzle, possibly by proxy, that makes them think they have a crucial perspective - and those points of view will conflict, giving each such participant a reason to bet. Taken in aggregate, you get a system that pulls in all those perspectives and distills a single signal out of them.
All evidence I’ve seen shows mainstream prediction markets devolve quickly into gambling and related corruption while predicting nothing other than conventional wisdom. especially about real-time facts. The prediction markets on the NBA Finals game four this year were completely useless.
The other value proposition would be that you could hedge your risk against all sorts of things that would otherwise be very difficult, like someone who sells funnel cakes hedging the risk of poor at the state fair due to rain. I think that's potentially interesting but was always far fetched and is definitely not as common as gambling.
If you want meteorological prediction, you are way better off buying meteorological prediction from a company that sells meteorological predictions.
Prediction markets could be interesting to hedge a bunch of weird little things. Alas, not how things have gone so far really.