Twitter Inc. has done something that was once thought unimaginable. It shut down one of its biggest attractions – Donald Trump’s account – and in doing so also canceled a sitting U.S. president.

The ban and public safety rationale behind it are part of a wave of crackdowns on the public digital spaces where the president’s most radicalized supporters congregate, and it comes in response to the violence and bloodshed of last week’s assault on the Capitol. Over the weekend, fledgling conservative social network Parler’s was effectively shut off by the technology giants it relied on to reach its user base – including its removal from Google’s and Apple Inc.’s app stores and the decision by Inc. Amazon Web Services to stop hosting Parler’s service. While the logic behind the actions was legitimate, the latest developments illustrate the power these companies possess as gatekeepers of content and information; their willingness to exercise that power opens a new chapter in the story of Big Tech.

Tae Kim is a Bloomberg Opinion columnist covering technology. He previously covered technology for Barron's, following an earlier career as an equity analyst.