This week in social media, Facebook opened up celebrity sharing to Instagram and Twitter while WhatsApp began testing voice calling. Meanwhile, Twitter's latest earnings report led to Wall Street's habitual dumping of the stock -- that is, until it was confirmed that Twitter had a deal with Google to begin including tweets in search results again.

It's time for Social Media Saturday!

Facebook:

Mentions Opens to Twitter and Instagram

Facebook just made it easier for public figures and celebrities with access to the special Facebook Mentions feature -- a lesser-known app Facebook launched last July to help celebrities and public figures connect with fans and other public figures -- to share posts across its rival platform, Twitter (as well as Instagram). Facebook's media blog explained this week that photos, videos, and updates in the Mentions app will come with options to share on Instagram and Twitter directly.

As we previously reported, Twitter recently took away the ability for verified users to post directly from Instagram with media previews, meaning they have to repost photos and videos on Twitter in order for their followers to see anything more than a link.

It's quite an annoying development. Perhaps Facebook opening up Mentions to cross-posting will alleviate some of the rival networks' escalating fence-building around celebs.

Instagram's Vine-like Loops Attracting Brands

Instagram announced this week that videos on the network can now loop, just like in Vine. It may sound like a simple case of feature cloning, but according to AdWeek, Instagram sees value in the looping feature with brands trying to reach out with nontraditional advertising.

Already, The Gap is using the looping videos (as well as more traditional platforms) to tell the "weirdest love story ever Instagrammed," in weekly installments as part of a lead-up to launching its new spring clothing line. According to Gap's media strategist, the video loops help expose Easter eggs and subtle twists and turns in its storytelling, hopefully leading to more engagement from interested viewers.

WhatApp Begins Testing Voice Calling

What may eventually be seen as the beginning of the apocalypse for wireless companies -- or at least a transformative moment in person-to-person communication using data over the Internet -- happened this week: WhatsApp began testing voice calling for mobile.

The Facebook-owned social messaging app has been working on voice calling for about a year now, but until this week there was no confirmation that the feature existed yet. Now, according to Mashable, WhatsApp has confirmed its testing the disruptive feature with a "small group" of Android users -- but with no word on the possibility of it being operational in the iOS app yet.

Of course WhatsApp won't be the first Internet messaging app to add voice calling -- Facebook's own Messenger app, along with Skype, Viber, and WeChat already offer similar support -- but the difference lies with how hugely popular WhatsApp is.

Last month, for example, WhatsApp hit 700 million monthly active users, which is about twice as many as a year ago, and getting closer to that one billion figure that Facebook CEO Mark Zuckerberg confidently predicted when shelling out an unprecedented $19 billion to acquire the company a year ago.

Those 700 million users across the world exchange 30 billion messages through the Internet every day, which is already a big threat to SMS messaging as a money-making feature for wireless carriers. Now just imagine the near future, when many of those users' calls are made through WhatsApp using data or Wi-Fi -- not wireless minutes.

Twitter:

Mixed Reactions to Earnings Report

Twitter released its quarterly earnings report, which showed big gains in revenues (nearly doubling its revenue from the previous year) but -- once again -- disappointing growth in its userbase.

According to USA Today, active users were up less than five percent from the previous quarter, which led to a disappointed reaction by investors on Wall Street, Twitter placing the blame on issues with bugs in Apple's iOS 8 and more speculation about CEO Dick Costolo's shaky future leading the company.

Google Search Integration Confirmed

However, later in the week, Costolo confirmed a rumor that Twitter and Google had made a deal to incorporate tweets into Google searches, according to TechCrunch, meaning more non-users getting exposed to Twitter as a content platform (and the return of a Google search feature sorely lacking for breaking news junkies).

It will also bolster an audience metric that Twitter has been trying to get Wall Street to take seriously for a few months now -- the "logged-out" userbase, or the approximately 600 million people who "use" Twitter for information, but never registered or tweeted themselves.

Coincidentally, Business Insider reported that Twitter's stock jumped 12 percent the morning after confirmation of the rumor, which could either be attributed to the Google deal, or possibly investors realizing that their collective habit of dumping Twitter after each quarterly report's "active userbase" metric inevitably disappoints may have led to an undervaluing of the stock.