The people who leaked the news to the New York Times apparently also said:
Instagram co-founders Kevin Systrom and Mike Krieger are resigning from the company they built amid frustration and agitation with Facebook CEO Mark Zuckerberg’s increased meddling and control over Instagram, according to sources.
The duo, who founded Instagram 2010 and sold it to Facebook in 2012 for $1 billion, told Facebook executives today that they were leaving the company, according to The New York Times. The co-founders have disagreed with Zuckerberg on a handful of recent product changes, including changes to comments and how posts are shared between the two networks.
I'm not surprised at this and it sounds right based on the few people I know inside the company. What I don't know is why the two founders were down the org chart and not on the board. It could be that they didn't want to be, who knows, or that Facebook didn't value them that highly.