There have been 6 heads of product at Twitter in 6 years

Jack Dorsey is the new de facto head of product at Twitter.

On Sunday, four executives left the company, including Kevin Weil, senior vice president of product.

It's part of a major shake-up, as Dorsey - founder and CEO - attempts to revitalise the struggling social network's fortunes.

Twitter has confirmed that it isn't hiring a replacement for Weil - meaning that Dorsey and the executive team will have to step up.

It makes sense: Though Dorsey helped found Twitter, he spent several years away from the company. When he returned in late 2015, replacing Dick Costolo, the hope was that as a founder he would have the authority to make the sweeping changes necessary to invigorate the platform.

But Weil's departure also highlights Twitter's schizophrenic approach towards its core product - in six years, it has now had six different heads of product.

This was first noted on Twitter today by Rich Greenfield, an analyst at BTIG.

First, we have Jason Goldman. He stepped down in December 2010. (He's now chief digital officer at the White House.)

Next, there's Satya Patel. He joined in March 2011, and left in June 2012. TechCrunch reported at the time that it was due to a re-organisation, with the ads and product teams splitting. "Patel's options were to take one of those roles instead of continuing to run both," wrote Eric Eldon. Patel is now a VC at Homebrew, a seed stage venture fund.

Third: Michael Sippey. Sippey joined in 2012, and left in January 2014. In an email, he said it was "time to move on." Prior to his departure, there were reports that it was difficult to get changes made to the product. Mike Isaac, then writing for AllThingsD, reported: "Where [Facebook] is willing to 'move fast and break things,' sometimes pushing out new features in the span of weeks, changes to Twitter's core product often languish for months - or even years - in limbo."

After Sippey came Daniel Graf. He made it less than a year in the role, quitting Twitter December 2014 after he was demoted in October that year . A source claimed to Re/code this happened because his "internal presentations lacked conviction and that he hadn't shipped any products since taking over the role."

Graf was replaced as head of product by Kevin Weil. Weil had been at Twitter since 2009, gradually moving his way up the ladder. He announced his departure last Sunday, along with several other execs. He says he's going to be spending more time with his family.

And that brings us to Jack Dorsey. Cofounder of Twitter, he was pushed out by the board in 2008, two years after the social network's genesis. He went on to found payments company Square in 2010, and continues to be CEO of the company even after his return to Twitter in 2015.

This kind of churn isn't unique to Twitter's product team. Along with Weil, executives Alex Roetter (SVP of of engineering), Katie Jacobs Stanton (VP of global media), and Brian "Skip" Schipper (VP of human resources), as well as Jason Toff (general manager of Twitter-owned Vine) all left the company on Sunday.

Their departures mark a very significant shake-up - the four (discounting Toff) made up 40% of Twitter's 10-man executive team.

Alongside Dorsey, COO Adam Bain, general counsel Vijaya Gadde, chief accounting officer Robert Kaiden, CTO Adam Messinger, and CFO Anthony Noto remain.

Bain, as well as Messinger, will take on new responsibilities in light of the departures, Dorsey has said. Bain will have "responsibility for the revenue-related product teams, the Media team, and the HR team on an interim basis," Dorsey said, adding, "Our CTO Adam Messinger will be taking over all of engineering and consumer product, design and research user service, and Fabric into one group."

In a note published Tuesday, Goldman Sachs analysts highlight the elevated turnover in other C-suite positions. Twitter has had three chief financial officers in four years, and three heads of engineering in three years (four, if you count Messinger taking on engineering responsibilities).

Twitter is struggling to prove to investors that it is able to attract new users and turn a profit. Its stock has been in near-constant decline since its IPO in 2013. After highs of $69 (£48) in January 2014, it has now cratered to the $16.50 (£11.50) mark.