The co-founder of the world's largest social-media business saw his fortune fall US$3.3 billion (NZD$4.5b) on Saturday (NZ time) after he posted plans to shift users' news feeds toward content from family and friends at the expense of material from media outlets and businesses.
As part of the shift, Facebook pages run by publishers and businesses may see a reduction in the number of people they reach and site visits, he wrote.
European Union competition chief Margrethe Vestager on Friday (Saturday NZ Time) said allowing advertisers to tailor political content to personal tastes on social media such as Facebook was a danger to democracy, according to interview in Vienna's Der Standard newspaper.
Many news organizations, bloggers and businesses have grown reliant on Facebook to spread information - articles, videos, infomercials - to their followers without paying for ads.
What will change, however, is the way Facebook prioritizes what to show you first.More news: K Sivan is new ISRO chairman
Now Facebook wants you to think about making sure your post is extra meaningful, and what the meaning of meaningful might mean to you, but most importantly what it means to Mark Zuckerberg's algorithm.
"It's obvious that the days of getting exposure as a business on Facebook are coming to an end", said Michael Stelzner, the CEO of social media marketing company Social Media Examiner.
"They're definitely going to be required to buy an ad", Schiffer said. In that vein, it's unclear for publishers how Facebook's rules on "meaningful" content will affect them. People will likely spend less time on Facebook as a result, the company says.
More clicks mean the posts would move higher in people's news feeds, even if people don't really want to see them.
The changes promised aren't entirely new - Facebook has been shifting the content on its news feed toward posts from friends and family and away from brands and publications for more than a year. Less time, of course, means fewer advertising eyeballs at any given time.More news: Oil crosses US$70 threshold in London as worldwide glut dwindles
Some hedge funds used Friday's drop in Facebook's stock to bolster their positions, said Joel Kulina, a senior trader at Wedbush. In this charged atmosphere, agents working for a Kremlin-linked company, the Internet Research Agency, disseminated content that reached an estimated 126 million users in the United States in 2016, Facebook revealed to Congress during hearings on the matter past year.
For media companies, a reliance on the company as a driver of traffic has proved an unreliable business model, given that it can change what it prioritizes in its News Feed at any time.
"This is understandable as brands and publishers have spent a lot of money over the years to build a presence on the platform and supplied Facebook's walled-garden with content to fuel its News Feed".
The algorithm changes will nearly certainly affect ad-supported media companies like BuzzFeed and Bustle, which depend in part on Facebook to bring in an audience.
A USA Today/Suffolk University poll published in October found that Americans believed by a two-to-one margin that Facebook should have done more to identify and reveal the Russian ads.More news: King supports president's signing of act to keep opioids out of US