[honest_guy]

> but it seems to me this would also be a problem for a hypothetical "blockchain" gambling system.

It depends what form of gambling you're referring to.

A blockchain based roulette smart contract could provide absolute transparency to anyone placing a bet. The exact process which determines the outcome is known, and it cannot be changed. The assurance that you get your money is the smart contract.

A smart contract based prediction market, such as Augur, can offer similar transparency. You have the assurance that, should the market be resolved in your favour, you will get your money. The main concern is the governance structure which determines the outcomes.