Yesterday, Business Insider chief correspondent Nicholas Carlson stuck a subtle shiv into his competitors at Buzzfeed, attributing the site's success in exploiting Facebook's ever-evolving newsfeed algorithm to its practice of buying traffic in the form of Facebook ads—as opposed to, you know, attracting readers. Then he took it out. Without telling anyone.

In the post, Carlson laid out a compelling explanation of how Facebook revisited its newsfeed algorithms, changing how it selects the stories you see. That recent change seems to have taken the piss out of some of the web's biggest new viral sharing sites: The shift drove down traffic for Upworthy, ViralNova, and other sites that traffic exclusively in sharebait.

But not Buzzfeed: It has actually seen traffic growth. Carlson's explanation for the anomaly was simple: Buzzfeed pays for play. It is known to buy Facebook ads for posts that it thinks needs "viral uplift." After considering and then dismissing Buzzfeed's "respected journalists who publish hard news" as a potential reason for its continued Facebook success, Carlson concluded:

It could be that Buzzfeed, unlike all those other sites, buys traffic from Facebook.

Buzzfeed's business model is to create advertorials on Buzzfeed.com and then get traffic to these advertorials by buying Facebook ads.

If that's the reason, then the message Facebook is sending isn't so much that it wants "high quality" content for its News Feed. It's that if you are a media company, and you depend on Facebook for your traffic, you better make sure Facebook is benefiting from your existence.

That's how the piece originally ended: with the sense that Buzzfeed's ability to financially reward Facebook helps explain its recent success on the platform.

But at some point, Carlson changed the story's ending substantially, with no note that he'd done it. Here's how it reads now:

It could be that Buzzfeed, unlike all those other sites, buys traffic from Facebook.

Buzzfeed's business model is to create advertorials on Buzzfeed.com and then get traffic to these advertorials by buying Facebook ads.

If that's the reason, then the message Facebook is sending isn't so much that it wants "high quality" content for its News Feed. It's that if you are a media company, and you depend on Facebook for your traffic, you better make sure Facebook is benefiting from your existence.

More likely, it's that, unlike all those other sites, Buzzfeed employs several respected journalists who publish hard news and smart analysis. Maybe, in the eyes of Facebook executives, this makes all Buzzfeed content "high quality" and therefore News Feed-worthy. Other sites, including Slate, The Atlantic, and Business Insider, have also invested in journalism and continue to benefit from Facebook traffic.

All of a sudden, it's not pay-for-play. Instead, Facebook is rewarding Buzzfeed—and a couple of other sites, including his own—because its "smart analysis" makes the content better.

Carlson confirmed the change on Twitter:

In an email exchange, he also confirmed that he changed the post after receiving an email from Buzzfeed CEO Jonah Peretti, and after discussing things with Business Insider chief Henry Blodget.

These are the facts:

1. I changed the emphasis after speaking with Joe and Henry, and considering what's happened to Slate and The Atlantic.

2. During this discussion or maybe before, Peretti had emailed me. But I didn't change the story because Peretti emailed me.

3. It didn't happen in this case, but I am open to being emailed by people and being convinced by their winning arguments.

This morning, Carlson posted a followup story based on his exchange with Peretti. Its title was "Buzzfeed CEO: Here's Why Facebook Isn't Crushing Us." Spoiler: It's not because they pay Facebook money. It's because they are awesome.

Update: After this post was published, Nicholas Carlson added a note to his original story, highlighting the changes for his readers and explaining his reasoning behind them. It reads, in part:

Peretti didn't say so, but I could tell he was annoyed about me speculating that Facebook treats Buzzfeed better because its an ad partner. But I still believed that to be a possibility. So I left the speculation in the story. I repeated it in a second post this morning.

I am sorry for not explaining why I made these changes in an update when I made them. I assumed that since I had not changed any reporting or corrected any facts – only switched the order of two pieces speculation, giving one more emphasis — that I had not needed to. Maybe I was wrong.

I also thought such an update would be boring for all but a few dozen active Twitter users. I still think this is true.

[Photo credit: AP]