Arthur Hayes, co-founder of BitMEX, has criticized BlackRock's IBIT ETF, suggesting it does not reflect long-term institutional confidence in Bitcoin. Hayes argues that major financial players, such as hedge funds and bank trading desks, are primarily engaging in basis trading. This involves buying ETF shares while shorting Bitcoin futures to exploit yield spreads, rather than holding Bitcoin for the long term. Hayes warns that ETF inflows and outflows are often misleading, driven by arbitrage rather than genuine demand. He notes that with narrowing futures spreads and reduced liquidity, ETFs are now seeing outflows, which could exert downward pressure on Bitcoin prices.