I always think that the sign of a good system (be it a country or a company or whatever) is not that mistakes don't happen. But that the same mistakes don't happen twice.
It's not as simple as don't have a school gathering under a landslide risk after heavy rain. The tips were a known danger. The mistake was in preventing their removal. This mistake happened because those at risk didn't have the power to act in their own interest. Preventing such mistakes in the future would require empowerment of the proletariat.
