Here's a simple theoretical example. People operate under a common, universal law system that defines the most basic rights. The rules of this system are only those which everyone who participates can agree to. For example, everyone agrees not to kill each other. People who do not accept these rules can form alternative societies, but they will not be able to access areas under common law through the use of smart locks and the like which restrict access to public spaces only to those who accept basic terms of behavior.

These rules can be under constant revision because the code that runs the base social platform is publicly audited, and anyone can submit a request to edit it. These revisions can be tested at smaller scales just by running the rules in private spaces. In your home, you can set whatever rules you want, but anyone running software with conflicting preferences will be alerted to the changes when they enter. If your home rules become popular with your friends, they may choose to implement them in their home. If enough people adopt them, the community may choose to implement them in certain spaces, and they can propagate outward.

The basis of this type of system would be mutual consent, and what a person consents to do can be adjusted at any time by their own software. It would be important that a person's personal platform was entirely under their control and only interacted with the outside world through approved protocols. Likely this would require a direct brain connection that could not be hacked because of physical safeguards.

Business could be conducted between communities that operated under entirely different rules through automatic contract negotiation. New ideas could spread from private to public spaces automatically through smart social contracts.

This is just one, very basic example of a society run by smart contracts. There's plenty of ways for these types of systems to be exploited, but that's part of the design process of any system. Particularly difficult is the problem of letting a machine which can be manipulated dictate so much of life.

But people's brains can be hacked already. Look at advertising, religious cults, mob mentality. People have always been vulnerable to manipulation, and we have developed an interconnected financial system where almost anything can be bought, especially power. We can learn from existing flaws as we develop new systems to fix the bugs in our biology and political systems that have made us vulnerable. We will definitely introduce new vulnerabilities. We just have to make sure we have a robust plan for continued development to respond to them.

I have no doubt that every new technology invites exploitation, and you're right to think about the consequences. That's an essential part of the design process of any technology, especially one that's general useful. That's the reason why we have such complicated software licenses.

But EvilCorp doesn't need smart contracts to send robots to steal your children. It will definitely use them if they're convenient, but they could just as easily go with the traditional human blood on dead trees contract that's ensnared many souls. Smart contracts add very little to their already efficient operation. But the people who can't afford to hire lawyers, bribe the police, and build robot armies will benefit a lot from enforceable contracts that don't require huge resources to enforce for purely digital transactions.