Scary charts once again dominated the future of news yesterday when both Forbes and BuzzFeed wrote about what appeared to be sharp declines in the use of Facebook social reader apps — the frictionless-sharing, “tell all my friends I just read about Snooki” apps that spread stories socially. The data seemed to show active users of social reading apps from The Washington Post, The Guardian, and others had began to plummet in April.

Readers have grown weary of the invasive, annoying apps! Hurrah! Or: Social readers are not the traffic boosters publishers once thought! Panic!

Or, maybe not. TechCrunch last night wrote that the drop is more likely due to tinkering on Facebook’s part on how shared articles are displayed to friends — specifically, a shift to displaying trending articles on the site rather than a “recently read articles” module. This was backed up by a tweet from the Post’s engagement producer:

Social reader “collapse” is b/c of evolving FB modules. Before: “double-double,” 4-5 stories down in a list, w/ friend icon – drove growth. — Ryan Y. Kellett (@rkellett) May 7, 2012

While the Post got most of the attention for its drop in numbers, The Guardian has as least as much skin in the Facebook game. In March Facebook sent more referral traffic to the Guardian than Google — a huge shift. That month, Facebook touted The Guardian as one of the success stories from using the Open Graph, with more than 3.9 million monthly active users, “over half of which are under the age of 25.”

I checked with The Guardian to see how they interpreted the drop — specifically, I asked Tanya Cordrey, director of digital development for the Guardian, who announced the company’s success with Facebook two months ago. Cordrey said over email they expected fluctuating usage patterns from readers, but something had indeed changed recently (emphasis added):

We’re still learning a lot about our Facebook app, and as with all brand new content platforms, we always expect fluctuating degrees of usage. Since our app launched in September last year we have repeatedly seen upswings and downswings in use depending on the type of content being shared by users, and the way that this user activity has been displayed within Facebook. Major changes made in the last month or so by Facebook have indeed resulted in a fall in usage since early April. However, this is not a signal that users are “abandoning” social reader apps, rather that articles which were previously surfaced predominantly in a user’s newsfeed are now much less visible.

Cordrey seems to back up the Post’s argument. (Though at Inside Facebook they found not all publishers are seeing the same decline.) It shouldn’t be a surprise that Facebook wields that much power, but it does make for a good reminder of the pact media companies make when they attach themselves to any third-party platform in an effort to help reach new audiences or just increase traffic. Google isn’t the only tech giant who can, with a simple internal decision, send a site’s traffic soaring or dropping.