Leading one of the most high profile technology companies in the world is not easy. Dick Costolo took over Twitter when it was a $1bn company.
Today it is a $24bn company, yet the former improv comedian has been forced to step down in the face of increased pressure from investors and shareholders.
So, given the fact that Costolo oversaw an incredible period of growth for the social network, who would now want to take on what looks like the difficult job of running Twitter, appeasing its ever-increasing user base while keeping shareholders happy by growing revenue?
Here is a list of those from within Twitter who could succeed Costolo, as well as a list of outsiders who could be brought on board to refresh the company.
- Jack Dorsey
Twitter followers: 3 million
The frontrunner for the top job, co-founder Dorsey was the CEO until October 2008 when he was apparently let go because he was spending too much time doing yoga. Dorsey will take the reigns temporarily on 1 July, but sources told the New York Times that ever since being ousted as CEO in 2008 he "has wanted to return to the helm of Twitter".
Dorsey is currently CEO of mobile payment company Square but Twitter is a much bigger draw and with with the founder-as-CEO story an appealing one, Dorsey returning to the helm makes for a very tantalising narrative. Whether he can turn Twitter around is unclear.
- Biz Stone
Twitter followers: 2.47 million
Another co-founder, Biz Stone left Twitter in 2011 and has since helped establish Medium with fellow co-foudner Ev Williams, and is now promoting his new app Super, with which he hopes to "inspire empathy". IBTimes UK spoke to Stone days before Costolo's shock resignation and he gave no indication that he was looking to get back involved, though he remains resolutely upbeat about the company's future.
- Ev Williams
Twitter followers: 1.82 million
Like Dorsey, Williams is a former Twitter CEO, handing the reigns to Costolo in 2010. Williams remains involved as a board member at Twitter though he is also actively developing his blogging platform Medium. As a former CEO, it is clear that Williams has the experience of running the company, but considering the complex challenges of balancing user needs with those of shareholders - something he doesn't have experience of - it is unclear if he has skills to turn Twitter's fortunes around.
- Anthony Noto
Twitter followers: 19,000
Moving away from the bigger names, Anthony Noto is the company's chief financial officer and was Costolo's right-hand-man in recent years. A former Army Ranger and ex-Wall Street banker, Noto has only been at Twitter since July 2014 and while his credentials suggest he could help drive revenue growth, there has been little indication of that to date.
Another issue is that Noto is not exactly seen as a big Twitter guy, with Business Insider quoting one former employee as saying "There could not be a guy who is less the spirit of Twitter than Noto." The CFO has also shown a lack of affinity with the product itself, sending several public messages that were clearly meant as DMs.
- Adam Bain
Twitter followers: 68,300
The head of revenue and partnership at Twitter, Bain is widely credited as creating the Twitter ad business from scratch. Bain has been at the company since 2010 meaning that he is one of the few members of the executive team to last that long, and has built up a good reputation among employees at the company. As CEO, Bain would need to show a vision for Twitter which he hasn't been required to do so far, but some of the tools he has overseen the creation of for advertisers hint at an ability to think about product as well as sales, and he is also thought of as a good communicator inside the company.
- Sheryl Sandberg
Twitter followers: 172,000
The chief operating officer at Facebook, Sandberg is one of the most powerful figures in the technology world, listed among Time's 100 most influential people in the world. Jumping ship from Facebook to Twitter is highly unlikely, but if the former Google executive could see the move as a new challenge and may relish the prospect of going toe-to-toe with boss Mark Zuckerberg in the world of social.
- Marissa Mayer
Twitter followers: 1.02 million
The Yahoo CEO is about to enter her fourth year in charge of the troubled web portal and while her efforts to turn it around have seen some success, the company is still struggling. Mayer is adamant that she is at Yahoo for the long haul so for a move to Twitter, she would need to be convinced that it had something to offer she currently wasn't getting at Yahoo.
- Vic Gundotra
Twitter followers: 16,400
Vivek "Vic" Gundotra is a former Google executive who built Google+ from the ground up. Now it is a matter of personal opinion if you see this as a positive or negative for his CV, but since leaving Google in April 2014, the former Microsoft employee has been quiet, but could he come from nowhere to take the top job at Twitter - even if he hasn't used his Twitter account for almost four years?
- Ross Levinsohn
Twitter followers: 5,300
Former Yahoo CEO, Levinsohn is on the shortlist from analyst Bob Peck who was among those calling for Costolo's resignation. Levinsohn is currently a board member of mobile advertising solutions company Millennial Media which could come in valuable if he was appointed as CEO of Twitter. Levinsohn's appointment would be an odd one however considering his standing would have been dented following his time at Yahoo but he remains a popular pick from analysts.
- Kevin Systrom
Twitter followers: 73,800
The man who made people want to share square images altered with filters, Instagram founder Systrom is still in charge of his photo sharing app despite it being purchased by Facebook for $1bn in 2012. Systrom could be looking for a new challenge, but the fact that Twitter no longer shows Instagram images in its tweets may be a sore point for the CEO.
- Mike McCue
Twitter followers: 17,700
The CEO and co-founder of Flipboard, McCue is another of Peck's Picks. McCue is old-school internet technorati having sold his first company Paper Software to Netscape back in 1996 for $20m. He is best known currently for his news magazine app Flipboard, which creates beautiful looking magazines from various online sources - including Twitter.
- Snoop Dogg
Twitter followers: 12.3 million
If the search was based on Twitter followers alone, then the Dogg would be head-and-shoulders above the competition. A lack of experience running a technology company may be a drawback but just think of the staff parties.