Robinhood Q4: revenue of $363M, up 14% YoY, 2021 revenue of $1.82B, up 89% YoY, net loss of $423M, MAUs up 48% to 17.3M; stock down 14%+ on weak Q1 guidance — Stock-trading app Robinhood gave a bleak revenue forecast for the first quarter of 2022 on Thursday. — Shares of Robinhood tanked 9% in after hours trading.