Regarding banks etc. I think after the GFC Mach I the government guaranteed peoples bank accounts. I'm not to sure how much of a balance they guaranteed or if this is still in force? Maybe someone on here may know the answer to that. I follow your line of reasoning and have considered the hypothetical scenario regarding our bank exposure.
Maybe if people are spooked enough and they are worried about austerity etc. these sort of alternatives will look pretty tempting to the aussie tax payer:
