• Mark Cuban criticized Bluesky for becoming an echo chamber, warning it was driving some users away.
• Engagement on Bluesky has plunged since February, with far fewer daily unique users.
• Cuban questioned BlueSky's future, citing vanishing nuance and an absence of some topics.

Mark Cuban is sounding the alarm on Bluesky's declining engagement — and he's not pulling his punches.

In a series of Bluesky posts, the billionaire investor and entrepreneur criticized the platform for fostering an echo chamber that he said was driving users away and inadvertently boosting traffic back to Elon Musk's X.

"The lack of diversity of thought here is really hurting usage," Cuban wrote, linking to a Washington Post opinion piece headlined "BlueSky's decline stems from never hearing from the other side."

Once known for "great give-and-take discussions on politics and news," Cuban said Bluesky had become a monoculture where dissent was unwelcome and nuance was vanishing.

"Engagement went from great convos on many topics, to 'agree with me or you are a Nazi fascist,'" he posted.

A graph of Bluesky's unique daily posters supports his concern.

On February 28, Bluesky had more than 1 million unique users daily. Since then, engagement has plummeted, with June 7 and 8 hovering well below that peak at about 670,000 daily posters.

The Musk factor

BlueSky's rise accelerated following the election of President Donald Trump, whom CEO Musk backed financially, and after X introduced new terms of service.

Many X users migrated to Bluesky, with some 2.5 million joining in one week in November.

Some were seeking a friendlier, more open platform with less hate speech and misinformation, and more control over what content is shown in their feeds.

A startup, BlueArk, even sprang up to help users migrate their X/Twitter histories to Bluesky, porting over millions of posts and creating the illusion of continuity on a new platform.

At the time, Cuban told Business Insider he preferred Bluesky over alternatives due to its variety of content and growing engagement.

Now, some of the earliest and most visible converts, including Cuban, are questioning whether the migration created a new community, or just repackaged the same silos.

"Why would anyone stop using Twitter if the only topic that is acceptable to you is news and politics?" he asked.

Cuban also criticized the platform's culture, saying: "The replies on here may not be as racist as Twitter, but they damn sure are hateful."

Posts about AI, business, or healthcare — traditionally strong areas for Cuban — often gain little traction or were met with outright hostility, he added.

Cuban also questioned Bluesky's business model: "How does everyone suggest BlueSky survive as a business? Or do you not care?"

• The friendship between Elon Musk and Donald Trump publicly unravelled on Thursday.
• It all started when Musk criticized Trump's "Big Beautiful Bill."
• Here's what business leaders like Mark Cuban and Bill Ackman have to say about the breakup.

Amid a dramatic falling out between Donald Trump and his "first buddy," Elon Musk, some of the business world's most influential voices are weighing in.

The relationship between the president and his once-close ally imploded on Thursday as they clashed publicly over Trump's "Big Beautiful Bill."

Musk, who stepped down from his role at DOGE in May, took to X to criticize the bill, calling it the "Debt Slavery Bill" and the "Big Ugly Spending Bill."

In response, Trump fired back at Musk during a White House event. He also defended the bill on Truth Social, while threatening to cancel Musk's government contracts.

Musk saw his net worth fall by $34 billion on Thursday, per the Bloomberg Billionaires Index. Tesla shares were also down by more than 14%.

Here's what several business leaders have to say about the row.

Mark Cuban

Amid his feud with Trump, Musk proposed creating a new political party for "the middle" in a poll on X.

Mark Cuban appeared to endorse the idea, quoting Musk's post and replying with three check marks.

The former "Shark Tank" star previously said he's "not a fan of either party," but would run as a Republican if he wanted to join politics.

Bill Ackman

Hedge fund billionaire Bill Ackman voiced his support for both Trump and Musk on X, calling on the two to put aside their differences and "make peace for the benefit of our country."

Ackman, who had endorsed Trump for his 2024 presidential bid, wrote: "We are much stronger together than apart."

"You're not wrong," Musk responded.

Paul Graham

Paul Graham, cofounder of the startup accelerator Y Combinator, also weighed in on the public feud between the president and the Tesla CEO.

"A lot of people seem to be treating this as if it were just a beef. But the underlying allegation is a very serious one. If it's true, Trump is surely going to have to resign," he wrote in a post on X.

Graham did not specify what allegation he was referring to.

Hours before Graham made his post, Musk went on X and accused Trump of withholding information about Jeffrey Epstein.

"Time to drop the really big bomb: @realDonaldTrump is in the Epstein files. That is the real reason they have not been made public. Have a nice day, DJT!" Musk wrote on X.

Graham told Musk in February that he should work with the government "carefully" because it's not "just a company."

A representative for Graham did not immediately respond to a request for comment from Business Insider.

• Mark Cuban and Elon Musk don't always agree on politics.
• However, Cuban appeared to like Musk's idea for a new political party for "the middle."
• Musk proposed the idea on X amid his ongoing feud with President Donald Trump.

Billionaires Mark Cuban and Elon Musk seem to have found some common ground.

As the Tesla CEO's relationship with President Donald Trump blows up in real time on social media amid their clash over the "Big Beautiful Bill," Musk proposed creating a new political party for "the middle."

"Is it time to create a new political party in America that actually represents the 80% in the middle?" Musk asked in an X poll on Thursday.

Cuban, who has sparred with Musk on X multiple times on subjects ranging from DEI to Trump, appeared to endorse the idea, responding to Musk's post with three check marks.

Cuban did not immediately respond to a request for comment from Business Insider.

That Cuban is attracted to the idea of a new political party may not come as a surprise.

The former "Shark Tank" star and Cost Plus Drugs founder has previously expressed his dismay with both political parties. He once described himself as "socially centrist" while "very fiscally conservative."

During the 2024 election, Cuban campaigned heavily for former Vice President Kamala Harris, previously telling BI that he liked that she's "not an ideologue" and supporting her pro-business stance.

In January, when journalist Matthew Yglesias proposed a 2028 presidential run for Cuban, BI asked the billionaire if he'd seriously consider the proposal.

"No," Cuban responded.