Look across the Web and you see it. While content surfers “like” plenty of content, they’ve fallen hard for LinkedIn’s “inshare” tab. It’s long been true of business news, which users overwhelmingly share with their professional networks; but even at general interest sites such as Time and the Atlantic, the “inshare” is beginning to steal some of Facebook’s “like” button’s thunder.

What’s going on? It’s a tough question to answer without concrete data, and data are hard to come by. Comscore, for example, doesn’t have applicable metrics. Facebook declined to provide analytics for this story, citing its quiet period. And peHUB’s own parent organization, Thomson Reuters, hasn’t responded to requests for information regarding how users across its spectrum of properties share information .

Yet something is afoot. Andrew Lipsman, ComScore’s vice president of industry analytics, says he believes that the “trend you’re honing in on, and that I see, too, is a lot more ‘insharing’ going on now, which I think has to do with LinkedIn’s effort to turn its network into less of a utility and more of a content site.”

Indeed, LinkedIn has made colossal strides since launching LinkedIn Today, a widely visited destination that shows readers what their connections are reading, what their industry peers are reading, and what stories a wider audience outside of their industry is reading.

Among the stunning results publishers have begun enjoying since the service’s launch last March: BusinessInsider has seen more than a 50x increase in referrals from LinkedIn; Wired has seen a more than 20x increase; and average monthly referrals to the Washington Post have more than quadrupled. (The numbers, supplied to me by LinkedIn, are likely conservative, as they date back to September.)

Facebook — with 800 million-plus users to LinkedIn’s 150 million — is growing as a content platform, too, of course. Lipsman notes that “people are sharing more and more over time on Facebook” even while “business networking is really starting to emerge in a notable way.” (According to Comscore, people spend roughly seven hours per month on Facebook, compared with an average 19 minutes per visitor per month on LinkedIn, though Lipsman notes that new users tend to “mute” some of LinkedIn’s “growth effects” as new users “tend to be lighter users.”)

Still, what’s being shared, exactly, is crucial to Facebook’s future success. And while entertainment stories can compete with baby and wedding pictures for users’ attention, it isn’t clear what else can.

Forrester analyst Sucharita Mulpuru has long argued, for example, that Facebook will never become a major e-commerce player because tech vendors and other retailers say they rarely receive major benefits from Facebook (or other social networks). Dennis Yu, CEO of BlitzLocal, a privately held advertising agency in Denver, believes the problem has grown more accentuated since Facebook released its real-time ticker and Timeline. “The newsfeed has become too crowded. More objects means fewer people are seeing or engaging with brand content,” he says.

Meanwhile, a broader base of news stories  – the kind that might give advertisers useful clues about readers — may be getting crowded out, too, despite Facebook’s efforts to drive more widespread engagement by introducing new verbs into its users’ lexicon, including “recommend,” “read,” “watch,” “listen,” and “cook.”

“Some people have both personal and professional contacts on Facebook, but the ‘ordinary’ user may still see Facebook as a place where they want to share personal things,” says Oakland-based digital media analyst Greg Sterling. “In my case, I’m much more inclined to share on Twitter and [I'm] set up so things go to LinkedIn rather than Facebook. My sense is that too much anonymous, nonspecific content comes off as a spam problem on Facebook.”

As for the social news apps launched by Facebook last September, my own Facebook friends use them less than when they were introduced last fall — a pattern that Sterling says he has seen, too. “I don’t think people necessarily want everyone to know what they are reading,” he says.

“There’s just a culture that exists around communication and entertainment on Facebook [that’s very hard to change], where people aren’t going there to get commercial information as much,” says Sterling. ” And that’s problematic for Facebook, because as they go public, they’ll have to squeeze revenue from every corner they can.”

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