According to Edward Dowd, ratings agencies assigned AAA ratings to certain tranches of collateralized debt obligations (CDOs) before the Global Financial Crisis (GFC), highlighting how reliance on external ratings can mask underlying risk (source: @DowdEdward on Twitter, May 14, 2025). For crypto traders, this historical failure underscores the need for robust independent risk assessment in decentralized finance (DeFi) products and tokenized debt instruments, especially as more traditional financial products are being recreated on blockchain platforms.