Those predictions are just market data, market data is often very expensive (my data usage at work is probably about $100k a year and i'm not even a trader), I imagine polymarket will be too when they are more established.
Happens already. Selling market data is part of how they finance themselves.
>Those predictions are just market data,
Any kind of fraud is just market data when you pay enough for it.
Traders sometimes go to prison for insider trading. The wisdom of the crowd human when the crowd is following someone with insider information is deemed legal.