third parties only observe what's published in a blockchain. they can choose to disagree with blockchain. when all/majority third parties disagree with blockchain - it becomes irrelevant and worthless while some other branch of that blockchain becomes "the real one".
it's really not the same as having limited number of third parties proclaim which version of blockchain is correct.
but more importantly - one doesn't have to ask permission from any third party to publish their transaction either via internet or radio or satellite or morse code. if you still think trading in gold is safer/easier - i don't know what else to say.
