He could afford to hire 100,000 minimum wage employees for life.
But he doesn't, does he? In other words, Bill Gates is not using his wealth very efficiently; it would be more efficiently used if it were spread around. It's not his fault, exactly: no single person can be expected to make efficient use of $30 billion, or whatever his current net worth is. But the fact remains that it seems likely that there is some maximum level of wealth that a single person can make reasonably efficient use of, simply because a single person doesn't scale. If that's true, then that's an argument for altering the rules of private property if a single person accumulates wealth above that level.
As for incentives, I find it very difficult to believe that if, for example, we set a threshold net worth of $100 million and said that anything above that gets taxed away (of course it would be more complicated than that in practice, but let's keep it simple for this discussion), Bill Gates wouldn't have started Microsoft because, oh, well, he's only going to get $100 million from it.
But he doesn't, does he? In other words, Bill Gates is not using his wealth very efficiently; it would be more efficiently used if it were spread around. It's not his fault, exactly: no single person can be expected to make efficient use of $30 billion, or whatever his current net worth is. But the fact remains that it seems likely that there is some maximum level of wealth that a single person can make reasonably efficient use of, simply because a single person doesn't scale. If that's true, then that's an argument for altering the rules of private property if a single person accumulates wealth above that level.
As for incentives, I find it very difficult to believe that if, for example, we set a threshold net worth of $100 million and said that anything above that gets taxed away (of course it would be more complicated than that in practice, but let's keep it simple for this discussion), Bill Gates wouldn't have started Microsoft because, oh, well, he's only going to get $100 million from it.