“I believe this was the right decision for Twitter,” said Dorsey, adding that the company “faced an extraordinary and untenable circumstance, forcing us to focus all of our actions on public safety.”

But the action, he noted, came with perilous consequences in terms of fragmenting the online conversation as people flee to use different services that suit them politically, and giving companies like Twitter enormous unchecked power.

“This moment in time might call for this dynamic, but over the long term it will be destructive to the noble purpose and ideals of the open internet,” he wrote. “A company making a business decision to moderate itself is different from a government removing access, yet can feel much the same.”

Twitter banned Trump’s account, which boasted 88 million followers, last Friday after first suspending him for 12 hours the day of the Capitol siege. On Friday Trump again tweeted that he wouldn’t attend the inauguration, as well as saying that his supporters would not be disrespected “in any way, shape, or form.”

Twitter immediately dismantled his account, saying the tweets could incite violence.

Facebook has also banned Trump indefinitely, as has Amazon-owned video platform Twitch. Snapchat also said it would permanently ban Trump from its app late Wednesday. The company had already said last week that Trump was indefinitely suspended last week.

“In the interest of public safety, and based on his attempts to spread misinformation, hate speech, and incite violence, which are clear violations of our guidelines, we have made the decision to permanently terminate his account,” Snap spokesperson Rachel Racusen said in a statement.

Google-owned YouTube banned Trump’s account for seven days. Amazon’s web services division cut off the Trump-friendly social media site Parler, which was also removed from the Google and Apple app stores.

(Amazon founder and chief executive Jeff Bezos owns The Washington Post.)

Together, the swift actions by tech companies demonstrated their ability to silence or significantly dampen the speech of even the most powerful voices in U.S. society. They raised fresh questions about the power of tech companies — which Dorsey alluded to — and the balance between free speech and public safety, even as the moves were lauded.

Dorsey, along with Facebook CEO Mark Zuckerberg, is a strong proponent of building platforms that can encompass as many voices as possible. That latitude and pro-free speech stance was extended even further with politicians. Twitter — like Facebook — has long given exemptions to public figures regarding their hate speech policies on the grounds that what they said was newsworthy and worthy of public debate. The decisions last week, to effectively silence those voices, Dorsey pointed out, would have huge ramifications.

“They limit the potential for clarification, redemption, and learning,” he wrote. “And sets a precedent I feel is dangerous: the power an individual or corporation has over a part of the global public conversation.”

Rachel Lerman contributed to this report.