This week in social media, Twitter's CEO Dick Costolo stepped down as the company faces a life-or-death transition into an uncertain future. Meanwhile, Facebook Messenger hit a milestone, your News Feed now studies your reading habits, Google and YouTube launch into social video game streaming, and Snapchat finally introduces a security option that's standard for most top user account-based apps.

It's time for Social Media Sunday!

Twitter

Dick Costolo to Step Down as CEO in July

For the past 18 months since its IPO, Twitter has had a rocky relationship, at best, with its investors. In fact, Twitter's performance on Wall Street became so consistently bad recently -- Twitter's stock has dropped an average of 35 percent in the past nine months -- that analyzing how and why Twitter failed to impress investors has become something of a quarterly tradition for journalists tracking the company.

For Costolo -- Twitter's embattled CEO who led the company into its IPO in the first place -- the quarterly earnings reports became regular skirmishes in an ongoing, ever-intensifying siege waged by critics, investors, and Wall Street analysts against his continued leadership of the foundering company.

On Thursday, June 11, that siege was over, as Costolo finally relented and relinquished his position as CEO. Twitter co-founder, and the first person to ever send a tweet in 2006, Jack Dorsey will take Costolo's place on July 1 as interim CEO.

While Costolo will remain on the company's board of directors, according to CNET, the terms of his departure filed in an SEC document, including forfeiture of all unvested shares after July 1, suggest he was technically fired, though Costolo claims he began private discussions about his stepping down as early as the end of 2014.

Twitter's Troubled Future?

"I believe now is the right time for Twitter to focus on finding a new leader for the years ahead," said Costolo in conference call with analysts and media. "You want to do these things when the organization is strong, when it's robust, when there's a clear plan and a clear path forward. And that's where we are today."

Dorsey, who also heads mobile payments company Square and is not leaving that position during his upcoming time as chief of Twitter, will be taking the reigns at an increasingly precarious time for company. Within the company, employees are reportedly worried about a wide-sweeping shakeup, according to The New York Times, while skepticism about Dorsey's "polarizing" leadership style abounds without.

140-Character Limit Axed for Direct Messages

Coincidentally, at the same time Twitter announced Costolo's departure, the company's developer blog announced that Direct Messages -- Twitter's private messaging option -- will no longer limit users to the standard 140 characters, also starting in July. If the change is a signal of a coming rethink under Twitter's new CEO, it's an exceedingly inscrutable one.

"The new limit for DMs will be 10K characters," stated the blog post, though for practical purposes, that means DMs are now unlimited-length messages.

Facebook

In Facebook, News Feed Reads You

Mark Zuckerberg is tweaking the News Feed again, but this time the change is likely to be imperceptible for users -- at least at first.

According to Facebook's announcement, the News Feed will now take into account, not only whether you read and/or interact with a post (e.g., sharing, commenting, or liking), but also how long you spend viewing the story.

Essentially, Facebook's News Feed is reading you while you read through it. The new metric for data collection isn't as unusual or shady as you may think though: It's a common metric used by many websites, and especially by news publishers like The New York Times and Latin Post, to measure reader retention and impact. As such, it may also help News Feed better cater to users' preferences without requiring any additional input from them.

Facebook's addition of this metric to its News Feed engine is actually more surprising for the implied fact that Facebook wasn't already measuring reader retention, and its announcement is undoubtedly part of Facebook's recent "Instant Articles" feature and news site partnership initiative to publish news content natively within Facebook's platform.

Messenger Hits 700 Million Active Users

Forced on users or not, Facebook Messenger is growing rapidly, retaining active users, and quickly catching up to the world's leading social messaging app (also owned by Facebook), WhatsApp.

The company announced this week Messenger had grown to 700 million active monthly users, defined as people who send at least one message per month. That's up 300 million users from last November, and quickly catching up to WhatsApp's userbase, which currently stands at 800 million, according to CNET. Between the two, Facebook has 1.5 billion monthly users on messaging apps, with more than 1.4 billion Facebook users across the globe to boot. (Undoubtedly there's some overlap.)

YouTube Gaming: Google Takes on Twitch

This week ahead of the Electronic Entertainment Expo (E3 2015), the biggest video gaming conference of the year, YouTube announced "YouTube Gaming," a new app, site, and platform for live streaming video games, finding gaming videos, and challenging social game streaming site, Twitch.

YouTube is already a destination for pre-recorded Twitch videos, how-to demonstrations, walkthroughs, and gaming reviews, but the company felt its gaming features were weak compared to the competition.

Twitch, bought by Amazon last year for nearly $1 billion according to CSMonitor, has become a destination for a new kind of live online entertainment: Video gamers can connect with, and watch live streams of gameplay often hosted by budding media personalities with regular broadcast schedules and growing fanbases.

YouTube Gaming is launching this summer with the aim to coax that activity to its own turf. Google will preview the app and site at E3 next week.

Snapchat Finally Implements a Standard Security Feature

Snapchat, the multibillion dollar unicorn messaging startup with a reputation for taking cyber security (too) lightly, has finally added two-factor authentication to its Android and iOS apps. According to TheVerge, the security feature -- a long-standing standard for account-based platforms like Google, iCloud, Twitter, online banking, and much more -- will be available in the latest update.

It's the system that sends you a one-time code via email or text when you log on from an unrecognized device to ensure your account has not been hijacked by a hacker. Two-factor authentication is widely considered in the technology industry as a simple security option that significantly lowers the chance of a personal account breach.

To enable two-factor authentication in Snapchat, switch it on in settings and Snapchat will send a six-digit code via text message. You can also save a physical copy of a recovery code, also optional, in case your phone is stolen, lost, or breaks.