It appears that Facebook has settled on a central metaphor for the behavior of its 600 million users.

See an interesting article? Want your friends to see it too? Facebook’s offered up two primary verbs to bring action to that formless desire: “Share” and “Like.”

But the writing’s been on the wall for “Share” for some time. Facebook seemed to abandon development on “Share” in the fall. And on Sunday, Mashable reported that the remaining functionality of “Share” is being moved over to the much more popular “Like” button. (Clicking “Like” on a webpage will now post a thumbnail and excerpt of it on your Facebook wall, just as “Share” used to do. The old “Like” behavior made the links less prominent. It’s actually a pretty big deal that will likely lead to stories spreading more readily through Facebook.)

But I’m less interested in the details of the implementation than the verbs: sharing (tonally neutral, but explicitly social) has clearly lost to liking (with its ring of a personal endorsement).

There’s actually a third verb, “Recommend.” Unlike “Share,” it’s not its own separate action within FacebookWorld; it’s just “Like” renamed, with a less forceful endorsement. But it lives deep in the shadow of “Like” everywhere — except on traditional news sites, which have tended to stay far away from “Like.” I just did a quick scan of some of the web’s most popular news sites to see what metaphor they use to integrate with Facebook on their story pages.

“Share”: Los Angeles Times, ProPublica, Talking Points Memo, Reuters, ESPN, The Guardian.

“Recommend”: MSNBC, CNN, New York Times, New Yorker, Washington Post, Globe and Mail, Le Monde, El Pais, Newsweek, Telegraph, CBC.

“Like”: Gawker, Politico, Slate, Wired, Time, Wall Street Journal.

Both “Like” and “Share”: Huffington Post, Chicago Tribune.

Now, that’s an unscientific sampling. And, among those who use “Share,” some might have preferred the different functionality (although that difference has now disappeared). But looking at those names, it seems to me that many more traditional news organizations are uncomfortable with the “Like” metaphor that has become the lingua franca of online sharing. The “Likers” are more likely to be Internet-era creations; news orgs that existed 30 years ago tend toward the more neutral choices. (With a few exceptions.)

And that’s understandable: Newsroom culture has long been allergic to explicitly connecting the production of journalism and the expression of a reader’s endorsement. (Just the facts, ma’am!) And “Like” is awkward. When I click a button next to a story, does that mean I like the fact that “Tunisian Prime Minister Resigns,” or that I like the story “Tunisian Prime Minister Resigns“? But there’s no doubting the appeal of “Like,” which feels like a vote when “Share” mostly feels like work.

Facebook hasn’t announced that “Share” buttons will stop working any time soon, and there’s always “Recommend” sitting there as a milquetoast alternative for the emotion-squeamish. (Although technically “Recommend” presents most the same problems as “Like” — it can still be read as a fuzzy endorsement.) But there’s a bigger issue here, as news organizations — many of them traditional bringers of bad news — have to adjust to an online ecosystem that privileges emotion, particularly positive emotion.

I can tell you, anecdotally, that for our Twitter feed, @niemanlab, one of the best predictors of how much a tweet will get retweeted is the degree to which it expresses positive emotion. If we tweet with wonderment and excitement (“Wow, this new WordPress levitation plugin is amazing!”), it’ll get more clicks and more retweets than if we play it straight (“New WordPress plugin allows user levitation”).

For harder data, check out some work done by Anatoliy Gruzd and colleagues at Dalhousie University, presented at a conference last month. Their study looked at a sample of 46,000 tweets during the Vancouver Winter Olympics and judged them on whether they expressed a positive, negative, or neutral emotion. They found that positive tweets were retweeted an average of 6.6 times, versus 2.6 times for negative tweets and 2.2 times for neutral ones. That’s two and a half times as many acts of sharing for positive tweets. (Slide deck here.)

Facebook’s own internal data, looking at major news sites’ presence within Facebook, found that “provocative” or “passionate” stories generated two to three times the engagement of other stories.

Or take the Penn study by Jonah Berger and Katherine L. Milkman of The New York Times’ most emailed list. It found that “positive content is more viral than negative content,” but noted that it’s actually as much about arousal (speaking emotionally, not sexually) as anything. Content that you can imagine someone emailing with either “Awesome!” or “WTF?” in the subject line gets spread.

Here’s the thing: The way that news gets reported and presented is influenced by economic incentives. When publishers realized that Google search traffic was a big driver of traffic, you saw punny headlines swapped for clots of “keyword-dense” verbiage and silly repetitive tag clouds — all trying to capture a little bit more attention from Google’s algorithm and, with it, a little more ad revenue.

But I believe we’ll soon be at a point where social media is a more important driver of traffic than search for many news organizations. (It certainly already is for us.) And those social media visitors are already, I’d argue, more useful than search visitors because they’re less likely to be one-time fly-by readers. As people continue to spend outrageous amounts of time on Facebook (49 billion minutes in December), as Twitter continues to grow, as new tools come along, we’ll see more and more people get comfortable with the idea that their primary filter for news will be what gets shared by their friends or networks.

And that means a phrase like social media optimization will mean more than just slapping sharing buttons on your stories and telling your reporters to check in on Twitter twice a day. It’ll also mean changing, in subtle ways, the kinds of content being produced to encourage sharing. I’m not saying that’s a good thing or a bad thing — just that it’s the natural outcome of the economic incentives at play.

Does that just mean more listicles? Maybe. But I’d argue that, on the whole, figuring out how to make people want to share your work with their friends generates a healthier set of incentives than figuring out how to manipulate Google’s algorithm. Providing pleasure — pleasure that someone wants to share — is not an inappropriate goal. And when you broaden out beyond “positive emotions” to the idea of driving arousal or stimulation — positive or negative — the idea starts to fall a little more neatly into what news organizations consider their job to be.

Let’s be clear: I’m not saying that news orgs should become engines of happy stories or only focus on the most outrageous or enticing news. Their mission can’t be channeled exclusively in that direction. I don’t know what it will look like for a quality news organization to focus on making more sharable journalism; it’ll be up to the very smart people who work at them to figure out how to do that while defending their brand identities. But I do know that the role of social media is going to keep increasing, and with it will come increased economic pressures to maximize for it. They may not “Like” or “Recommend” it, but I suspect it’s a fate they’ll all, er, “Share.”