When Roku (ROKU -10.29%) went public, many investors scoffed -- and rightfully so: Any company producing hardware can quickly be undercut by the competition. Without a sustainable advantage over tech and media giants, how could a plug-in dongle possibly be a good investment?

Those naysayers were wrong. The stock has returned over 1,700% since going public in 2017. The key: the build-out of an advertising platform that's raking in users, viewing hours, and ad dollars. 

Motley Fool contributors Brian Stoffel and Brian Feroldi were among those doubters. In this June 28th video on their YouTube channel, they discuss that mistake, run the stock through the antifragile framework, and discuss if the stock is still a good investment today.