While I generally agree with your point, it seems to me like that specific scenario could be solved with a dead man's switch contract. Not ideal, but still better than other cases.
I got the impression that the answer you'd get from the Ethereum team is: at the worst case, this is just as bad/good as the current system - i.e. real world effects have to be mediated by an executing authority, same as a real world contract. They would add (and I agree) that smart contracts still have advantages, even in this case.
You're right, the dead man's switch is interesting here. I wasn't thinking about the ability to reference a fairly precise point in the future via block number instead of an external input to the system.
Don't get me wrong, I'm pretty excited about smart contracts. It just seems like there are a lot of things that we don't think much about currently because our current system is generally pretty forgiving in its fuzziness, but that could have big consequences (and introduce new incentives to act badly) in the world of script-controlled, irreversible contracts.
I got the impression that the answer you'd get from the Ethereum team is: at the worst case, this is just as bad/good as the current system - i.e. real world effects have to be mediated by an executing authority, same as a real world contract. They would add (and I agree) that smart contracts still have advantages, even in this case.