Mike Blake/Reuters Shark Tank investor Kevin O'Leary told The Pomp Podcast that bitcoin is too volatile and illiquid for his portfolio but he would like to own a cryptocurrency ETF. "Give me the top 7 cryptocurrencies, put them into an ETF wrapper, and let me invest in it with liquidity so that if I want to buy a million dollars of it in the morning and sell a million dollars in the afternoon, I can do that in an ETF format," he said.