Casa co-founder Jameel Jaffer has raised concerns about Bitcoin users reusing old public key addresses, potentially exposing around 4 million BTC, or 25% of the total supply, to quantum computing threats. Despite Satoshi Nakamoto's 2009 recommendation to use one-time addresses for enhanced privacy, many users opt for convenience, particularly in automated withdrawals. Jaffer highlighted that while the risk is significant, quantum computers capable of compromising Bitcoin's encryption are likely at least a decade away. He estimated the probability of such advancements occurring within that timeframe to be over 50%.