This is why I think taxes on the very wealthy should be so high that billionaires can't happen. The usual reasons are either about raising revenue or are vague ideas about inequality. It doesn't raise enough revenue to matter, and inequality is a fairly weak justification by itself.

But the power concentration is a strong reason. That level of wealth is incompatible with democracy. Money is power, and when someone accumulates enough of it to be able to personally shake entire industries, it's too much.