At a time when  Facebook appears to be looking to its acquired companies to ensure its continued financial success, the founders of those acquired companies seem to be looking for the exits. First to announce his departure was Jan Koum, co-founder of WhatsApp, who said in April that he was leaving, although some reports say he still appears to be on the books as a Facebook employee. Now Instagram's founders, Kevin Systrom and Mike Krieger, have announced that they will leave Facebook in the coming weeks, six years after the social network giant acquired their startup.

In a statement, Systrom simply wrote that he and Krieger are ready to move on to something new. 

"We're planning on taking some time off to explore our curiosity and creativity again. Building new things requires that we step back, understand what inspires us and match that with what the world needs; that's what we plan to do." 

Mark Zuckerberg said in a statement that he was looking forward to seeing what Systrom and Krieger do next, and has learned a lot from working with them.

It sounds like a very amicable breakup, at least based on the principal players' public statements. But some who were "familiar with the matter" told Bloomberg that the Instagram founders are leaving because of disagreements with Zuckerberg. In the past, Facebook had allowed Instagram to function autonomously, these sources said. But lately, Facebook's usage is dropping, perhaps as the result of scandals involving data privacy and Russian election influencing. Or perhaps because the social network's new policy of prioritizing messages from people you know over news stories in users' newsfeeds leads to less engagement. Either way, Zuckerberg seems to be increasingly looking to Instagram for continued growth, and the resulting scrutiny became an unwanted intrusion, sources said. With the founders gone, they expect Instagram will be more tightly integrated into Facebook, and may become more of a division within Facebook, rather than its own company.

Instagram's founders' leaving comes at a time when Instagram is attempting to become more of an e-commerce platform, with a newly announced shopping app. It's likely feeling some competitive pressure ever since its rival, Snapchat, announced a deal with Amazon that will allow users to point their smartphone cameras at an object--a pair of shoes, for example--and then buy that item on Amazon.

As for WhatsApp, only one of its two founders came along when Facebook acquired it in 2014. Jan Koum remained with WhatsApp, while Brian Acton took his money and bowed out. Earlier this year, Acton sharply criticized Facebook on Twitter in the wake of its data privacy scandal, calling on people to #deletefacebook. Around the same time Koum resigned, citing disagreements over Facebook's data privacy.

And so Zuckerberg, besides running Facebook, is left with two of the most successful social networks on the internet within his company. But the founders who made them successful aren't running them anymore.