In this week’s ‘Skim: why Facebook’s latest algorithm change serves as a stark reminder to advertisers that they don’t hold all the power; Facebook introduces a Pinterest-esque “Sets” feature; LinkedIn upgrades messaging—and your productivity—with smart replies; why Snapchat could soon became a legitimate source of referral traffic; all about Twitter’s new “transparency center”; why social commerce is coming and your brand needs to be ready; three tips to optimize YouTube videos; and much more…

Skim for this week’s social network news in a nutshell!

1. The Facebook algorithm change heard around the world

The social network this week quietly rolled out a six-country test that had all non-ad Page posts taken out of the traditional News Feed and buried in Facebook’s newly launched (and practically hidden) Explore tab.

As a result, many publishers’ referral traffic plummeted 60-80%, and engagement on some Pages in the six-country test block (Sri Lanka, Bolivia, Slovakia, Serbia, Guatemala, and Cambodia) declined four-fold from their usual levels.

Facebook’s VP of News Feed said the test won’t expand further—music to most social media marketers’ ears, certainly. But we think marketers should considers this latest experiment a notice that even though the social network can be an integral source of traffic and growth for brands, there’s no guarantee that traffic won’t all go up in flames. If Facebook decides users would rather see only friends’ posts in their News Feeds, you bet the cost of reaching your fans will increase.

2. Facebook gets Pinterest-ing with new “Sets” of posts

Pinterest fans could find pleasure in Facebook’s latest feature test. The social network is experimenting with what it calls “Sets,” themed groups of posts that let users collect various status updates, photos, and videos, and share them as a grouped collection with everyone, or friends of their choosing.

The feature could potentially make it easier for businesses to target more niche segments of their fans by posting only for specific groups of leads or fans, while Facebook could eventually monetize the product by offering a special button to let users add a product to their “Sets.”

Facebook is likely a way off from stealing Pinterest’s thunder in this space, but if it can happen to Snapchat, it can happen to anyone.

3. LinkedIn introduces smart reply technology to messages

upgraded its messaging platform to make it easier for users to respond quickly, hopefully increasing engagement and use of the platform’s messenger function. A bit like the iPhone, the company has used machine-learning to suggest up to three replies to users based on the content of the message.

The goal is to provide LinkedIn users with quick, relevant options for feedback to their networks, and the LinkedIn team says the replies will become even more personalized in the future. And, for now, your smart replies will be limited to English.

4. Snapchat could soon play a big part in your referral traffic

Thanks to a new update from the social messaging app, iOS users are now able to directly share links from other apps with individual friends or groups of users on Snapchat via the iOS share sheet.

This new ease of sharing of external links on the platform means users no longer have to copy and paste a URL; as a result, websites could gain traction in referral traffic from Snapchat…