Prediction markets, although this is becoming less necessary as governments come around to allow sports betting. Still, there are probably many markets that will never allow legal betting.
Maybe it's more than breaking the law. If I want to bet on something random, say, 'if it will rain tomorrow in my hometown', it's pretty hard to do without a blockchain unless I know the other party.
A prediction market could solve that, cheaply build consensus where it would be harder to do otherwise.
Weather derivatives are a thing, traded on CME. They have a centralized clearing function. It works nicely.
Prediction markets exist in many places with centralized exchanges/clearing houses. If there is enough volume, the market works, if there is not, it doesn't. They exist for most financial securities, commodities, sports, various weather events and probably many other things I'm unaware of.
They mostly use a central party and (i'll guess) a pretty standard sql database. Before the financial crises some of the trades were done bank to bank with (horror...) no intermediary.... like people just called each other and kept distributed records and settled up...
They work if your jurisdiction allows you to participate in them. If you live outside of the elite banking countries, you probably don't have access to these secure, liquid markets.
