This week in Social Media, Mark Zuckerberg announced he and his wife would donate 99 percent of their Facebook stock to charity, prompting critics to express a great deal of skepticism.

Meanwhile, Facebook began positioning itself against Twitter's Periscope by rolling out a new live video feature, Snapchat began broadcasting live events nationwide as the Bernadino shooting transpired, and Yahoo launched a refreshed version of its messenger.

It's time for Social Media Sunday!

Facebook

Is Zuck's $45 Billion Charity or 'Philanthrocapitalism'?

Facebook CEO Mark Zuckerberg made headlines by announcing after the birth of his first child that he and his wife would give 99 percent of their Facebook stocks, currently worth about $45 billion, to philanthropic initiatives.

To do so, they set up the Chan Zuckerberg Initiative, dedicated to "advancing human potential and promoting equality."

And that's when the controversy erupted. The Chan Zuckerberg Initiative was set up as an LLC, or limited liability company -- meaning it's not a charitable foundation or a nonprofit, reported The New York Times. The initiative can donate to charities, but it can also invest in companies for profit, as well as make contributions to political causes.

Also, the donation is in stock, rather than Zuckerberg cashing it out and then donating the value after taxes. Noting that fact, the New Yorker charged that Zuckerberg's giving 99 percent of his fortune wasn't charity, but "philanthrocapticalism" that allows Zuckerberg to avoid paying capital gains or estate taxes.

"The size and timing of the tax benefits to Zuckerberg and [his wife Priscilla] Chan are uncertain, but they are likely to be large," wrote the New Yorker's John Cassidy, adding that the initiative's LLC status allowed Zuckerberg to remain in personal control over where the money went, giving him outsized influence.

Zuckerberg responded to critics on Wednesday on his Facebook page arguing that the LLC structure was a common modern method of philanthropy that allowed for the "flexibility to execute our mission more effectively," adding, "in fact, if we transferred our shares to a traditional foundation, then we would have received an immediate tax benefit, but by using an LLC we do not."

Taking on Periscope with Live Video

Facebook has had a live video app for a while now. But that app, Mentions, was only available for public figures and celebrities.

Now that anyone can live stream video on Periscope, Facebook is essentially expanding Mentions to everyone in a new feature coming to the Facebook app called Live Video.

In its announcement, Facebook said it was rolling out the new broadcasting feature with a limited number of people on iOS, but it's not hard to imagine a broader rollout happening on iPhones and Android soon.

"Live lets you show the people you care about what you're seeing in real time," announced Facebook. "To share live video, tap on Update Status and then select the Live Video icon. ... During your broadcast, you'll see the number of live viewers, the names of friends who are tuning in, and a real-time stream of comments." Afterwards, the video will be posted on your timeline like any other video.

Sound a lot like Twitter's Periscope? That's exactly what Facebook plans to crush, whenever Live Video finally, fully goes live.

Snapchat

Challenging Moments

When the tragic mass shooting in San Bernadino, California occurred last week, Snapchat jumped on the chance to provide its users with up-to-the-minute updates in an organized fashion. For the first time, Snapchat's "Live Story" went live across the nation, with Snapchat curated images, video, and live updates from Snapchat users.

It's the unicorn startup's latest move against Twitter, which introduced a similar feature a few months ago called Moments. "We published this story because we felt we that the content, which comes form the L.A. Local Story, was newsworthy and held national significance," said Snapchat VP of communications Mary Ritti to Reuters. Normally Live Stories on Snapchat are restricted by location.

Yahoo

Same Name, New Messenger

Yahoo Messenger disappeared in the early half of this year, but it's back, and it's been revamped to better compete in the expansive world of social media messaging.

At least that's what Yahoo hopes, according to The Verge, which spoke Yahoo about the app's rerelease on iOS, Android, and the web. Yahoo says Messenger will soon serve as a connective layer for everything the company offers -- Yahoo News, Mail, Flickr, and even app streaming -- as it's been rebuilt with technologies from at least 10 companies acquired by Yahoo.

For now, it's aimed at family and group photo sharing, but Yahoo says it will be updating Yahoo Messenger with new features quickly and often.