None of these should cause a wealthy man to go bankrupt.
It can cause a business to go bankrupt, and a wealthy man to become much less wealthy, but otherwise either you are stupid or you are diversified; and it's easier to 'stay there' than to 'get there'. If a stock market crash or, say, Madoff hurts you then it's bad luck; but if it destroys you then it's stupidity.
For example, Bill Gates should still be wealthy even if Microsoft went completely bankrupt at any point since mid-1980ies. Sure, he probably wouldn't be on his malaria campaign in that case, but it wouldn't hurt his life that much.
It can cause a business to go bankrupt, and a wealthy man to become much less wealthy, but otherwise either you are stupid or you are diversified; and it's easier to 'stay there' than to 'get there'. If a stock market crash or, say, Madoff hurts you then it's bad luck; but if it destroys you then it's stupidity.
For example, Bill Gates should still be wealthy even if Microsoft went completely bankrupt at any point since mid-1980ies. Sure, he probably wouldn't be on his malaria campaign in that case, but it wouldn't hurt his life that much.