As for unintended consequences, someday something will go wrong with nanotechnology, as it has with electricity, cars, and computers. But we shouldnt deny ourselves the benefits of a new technology just because we cannot foresee every consequence. We should proceed by trial and error and ameliorate problems as they arise.
Armageddon may indeed be postponed indefinitely, but only if, with due caution, we leave human genius free to harvest the fruits of technological progress.
It's a stupid and irresponsible argument founded in technological hubris bordering on religious faith. He pretends that there is no consequence so serious that we can't invent a fix in time. There are any number of historic die-offs that attest to the fact that nature can indeed serve up consequences from which its victims do not recover.
Each invention carries risks, some of which are quite apparently lower than others. Insurance can do a dandy job of assessing whether a product is worth the attendant risks. Validation of the accuracy of product claims and risk assessments are necessarily the province of a third party. Patent applied for. :-) All we really need is tort reform.