Robinhood (HOOD) is expanding its prediction markets through a new joint venture with Susquehanna to operate a CFTC-licensed exchange and clearinghouse. This move aims to significantly grow Robinhood's fastest-growing revenue line, which has already seen 9 billion contracts traded by over 1 million customers. The author believes prediction markets could become a $1 billion business for Robinhood in the coming years, signaling strong potential for revenue growth.