> It's his money. He could buy a fleet of yachts, set them on fire, and upload the video footage - why shouldn't he be allowed to do that? At what arbitrary level of wealth does 'his' money become everyone else's money?
This is a good question to ask.
Typically arguments about the ethical demands of wealth are predicated on how that wealth is _acquired_. As a society we suppose that some wealth is acquired "fairly" (say through some amazing talent or hard work), while other wealth is said to be acquired "unfairly" (say through fraud or exploitation).
There's a separate question however that this does not address: regardless of how you have earned your wealth, to what degree are you morally permitted to _retain_ it? To frame the question is slightly different terms, if I am in possession of an expensive life-saving medicine, and my neighbor is in dire need of this medicine, am I morally obligated to give my neighbor this medicine? The question of _how_ I acquired this medicine is quite separate from the question of whether I have a moral right to retain it.
The same question may be asked of exorbitant wealth. If I have enough money to buy a fleet of yachts and set them on fire, and my neighbor does not have enough money to pay for her children's breakfasts, do I have a moral right to set those yachts on fire? Or am I morally obligated to surrender some of my wealth to my neighbor's hungry children?