Jack Dorsey has stepped down as chief executive of Twitter, but that didn’t stop him from taking a shot at other CEOs on his way out the door.

In a November 29 morning email announcing his resignation, Dorsey wrote that despite a lot of emphasis on companies being founder-led, he believed it was ultimately “severely limiting and a single point of failure.”

“There aren’t many companies that get to this level,” Dorsey concluded. “And there aren’t many founders that choose their company over their own ego.”

Founder-first culture is common in Silicon Valley. And besides seeming to compliment himself in his goodbye note, there are a number of tech leaders Dorsey could be referring to.

Mark Zuckerberg famously started Facebook, now known as Meta, in his Harvard University dorm room in 2004, and has remained CEO ever since. Over the past few years, Facebook has been the subject of a number of controversies, from the circulation and propagation of fake election news to the Cambridge Analytica scandal. This past year, criticisms of the company under Zuckerberg’s leadership have reached a fever pitch, with revelations that the company allowed high-profile users to bypass content moderation rules, and ignored deleterious mental health effects on teens. While there have been calls for Zuckerberg’s removal and criticism of his leadership style, he has publicly stated that he has no plans to step down anytime soon.

Dorsey has previously poked fun at Zuckerberg’s ambitions to focus his company on the “metaverse,” a digital world that blends virtual, augmented, and physical reality. Following Meta’s rebranding announcement, Dorsey seemed to agree with users on Twitter who said the metaverse could become a “dystopian corporate dictatorship.”

Elon Musk, who cofounded Tesla and SpaceX, currently serves as CEO of both. While doing so, he’s openly feuded with other CEOs and politicians, and has had serious run-ins with the Securities and Exchange Commission over his tweets. YouTube cofounder Chad Hurley took a jab at Musk last October on Twitter, deeming him a part of the “axis of ego” among figures like Donald Trump and Kanye West. Musk’s response: “Stop being a chad.”

Evan Spiegel founded social media company Snap in 2011 and has remained CEO ever since. Back in 2018, his leadership came under fire after company insiders called the culture “toxic.” That same year, Snap began to lose users and faced a falling stock price. In 2019, Snap’s chief financial officer and vice president of investor relations both stepped down after less than a year on the job after reports of clashing with Spiegel. At the time, critics warned that he was a victim of “founder’s syndrome,” the name for an apparent trend among young startup entrepreneurs who are reluctant to relinquish executive control to outside forces. Spiegel remains CEO to this day, and the company has since recovered—its revenue has grown 57% year over year, according to its third-quarter earnings report, and its community contains over 300 million users.

Some founders reluctant to step down have eventually been forced out. Travis Kalanick, who cofounded Uber in 2009, resigned in 2017 after dramatic pressure from some of its biggest investors. His departure followed reports of a workplace culture rampant with sexism and harassment, as well as a program that allowed the rideshare app to circumvent law enforcement, all of which happened under Kalanick’s leadership.

Although Dorsey has officially stepped down from his role leading Twitter, he has held on to his CEO position at Square, a digital payments company that he cofounded in 2009. Currently valued at $98 billion, Square reported disappointing third-quarter sales in November.

In his resignation letter on November 29, Dorsey praised Parag Agrawal, who will succeed him as CEO, and Bret Taylor, who will become board chair. He added that his decision to step away from the company was “a tough one,” but that it would change the company “for the better.”

“I know we’ll prove this was the right move,” he wrote.