Polymarket seems OK (or at least unethical for a different reason): the prize pool is entirely from the gamblers’ money, and evenly distributed to the winners.

Polymarket seems OK (or at least unethical for a different reason): the prize pool is entirely from the gamblers’ money, and evenly distributed to the winners. I don’t think Polymarket does this, but I also think it would be OK if the casino takes a cut of the prize pool, as long as it ensures that winners never receive less than they bet. For example, the casino may receive $losers/n (they pick n, $losers = total bets of losers), and winners receive $bet($losers(n - 1)/n + $winners)/$winners, $winners = total bets of winners, $bet = their bet). Then it’s “tails = I win you lose, heads = we both win someone else loses, except nobody wins if everyone gets heads but that’s extremely unlikely (especially with more than 2 options)”.