Roblox stock posted stomach-churning losses in Friday’s premarket, offering a valuable lesson for investors in companies that sell to children: what’s good for customers can be very, very bad for shareholders. Roblox stock was down 24% in premarket trading after the online gaming platform popular with children posted results following Thursday’s closing bell. The guidance for bookings was also revised down to a year-over-year increase of 8% to 12%, far down from a previous 22% to 26%.