Roku suffers worst week since debut as media-streaming wars spook investors

The promise of growth that has attracted investors to the Los Gatos, California-based company also drove its stock to lofty valuations

Roku Inc. investors just suffered their worst week since the company’s 2017 market debut as the stock fell victim to investor fears of looming media-streaming wars.

First it was Facebook Inc. showing off a new model of its Portal video chat device that can be connected to a TV and has access to Amazon.com’s streaming service. Then Comcast Corp. offered a device for its internet-only customers. By the end of the week Roku’s stock had fallen by 27%, wiping out roughly $5 billion of shareholder value.

The selling peaked on Friday after Pivotal Research Group started coverage of Roku, advising