Dick Costolo resigned as Twitter's chief executive Thursday, nearly five years after assuming the top job. He oversaw the company's initial public offering of stock and, subsequently, its shares' underwhelming performance. And as Twitter's user base skyrocketed, its CEO found himself at the center of more than one controversy.
Costolo joined Twitter as chief operating officer in September 2009, but he -- at least jokingly -- had bigger plans from Day 1.
A year later, he was running the show, taking over as CEO from Twitter co-founder Evan Williams.
In 2011, Twitter's public profile rose as protesters used social media to organize uprisings in Tunisia, Egypt and other nations in the "Arab Spring" movement.
The next year, Costolo was solidifying his management style ...
... but he drew fire after weighing in on several major websites' plan to hold a "blackout" to protest Congress' Stop Online Piracy Act and Protect IP Act, known as SOPA and PIPA -- bills that sites such as Wikipedia and Google claimed would amount to censorship.
Costolo also has taken some heat over the role of women at his company. In 2013, the New York Times published an article criticizing Twitter for its almost complete lack of women in top leadership roles, quoting an academic, Vivek Wadhwa, who called the absence a product of "elite arrogance" and "male chauvinistic thinking." Costolo responded by likening Wadhwa to a comedian known for his over-the-top persona.
Although the CEO later had a more nuanced conversation on the topic, the comment did not go over well.
Costolo also has been in the hot seat as Twitter struggles to control rampant harassment, including threats of physical violence and the publication of home addresses, by some users targeting other users.
Perhaps most important to Costolo's career, however, is that Twitter's earnings and stock price have not met investors' lofty expectations. After an initial public offering in 2013 that saw shares soar, the stock suffered a series of precipitous drops.
Although shares have recovered from their all-time low, it's been a bumpy ride, and investors did not forget who was leading the company.
Silicon Valley venture capitalist Chris Sacca, a Twitter investor, still had good things to say.
Regardless of the reasons, on Thursday Costolo was on his way out. Twitter co-founder Jack Dorsey will take his place at the company's helm during the search for a permanent successor, Twitter said.
The handoff, at least, was cordial.
For breaking news, follow @raablauren and @cmaiduc on Twitter.
READ MORE: Twitter CEO Dick Costolo to step down