Since 2005 The Huffington Post has built a media empire in large part on the backs of 6,000 unpaid bloggers, or “citizen journalists.” Some of them haven’t been too happy about the arrangement. Now that Arianna & Co. are cashing in on AOL’s $315M buyout, will the bloggers stick around? And what is the site worth without them?

All the commentary I’ve read today about AOL’s $315 million buyout of The Huffington Post seems to miss one huge, glaring, cover-it-in-highlighter sized problem. Paul Carr of TechCrunch probably has the most astute observations on the state of HuffPo, but he leaves out part of the equation. Carr writes:

“Arianna Huffington’s genius is to churn out enough SEO crap to bring in the traffic and then to use the resulting advertising revenue – and her personal influence – to employ top class reporters and commentators to drag the quality average back up. And somehow it works. In the past six months journostars like Howard Fineman, Timothy L. O’Brien and Peter Goodman have all been added to the HuffPo’s swelling masthead, and rather than watering down the site’s political voice, it has stayed true to its core beliefs.”

What Carr astutely picks out is that at the core of The Huffington Post’s business model is a high/ low dichotomy. There’s the low-level search optimized (SEO) content—the “crap” Carr mentions—and then the value-add high-level stuff like Howard Fineman. But as Carr points out, it’s the SEO “crap” that brings in much of the traffic, and therefore the revenue.

Writing for Slate, Jack Shafer describes how HuffPo has used this strategy to win more traffic—and revenue—than Slate:

HuffPo pulled off one of the greatest acts of SEO whoring in the history of the Web yesterday. If you Googled the query, “What time does the Super Bowl start,” the first return was a HuffPo “article” titled “What Time Does The Superbowl Start?” And lest the search engines miss the germ of what was clearly a trending question, the first three paragraphs of the HuffPo posting read: Are you wondering, “what time does the Superbowl start?” It’s a common search query, as is “what time is the super bowl 2011,” “superbowl time” and “superbowl kickoff time 2011,” according to Google Trends the evening before the Super Bowl. It’s easily answered too. Super Bowl 2011 will take place on Sunday, Feb. 6, 2011, at 6:30 p.m. Eastern Time and 3:30 p.m. Pacific Time.

This is clearly not the kind of high-value editorial content Huffington Post pays top dollar for Howard Fineman to write. Rather, built into Huffington Post’s infrastructure is a web of over 6,000 unpaid bloggers—or “citizen journalists,” as the site calls them—who have been cranking out material for free since its inception in 2005. Some write because they support the site’s progressive political mission, some try to use it as a springboard to jump-start careers in journalism.

And the bloggers’ content isn’t all SEO “crap.” Some of this army of 6,000 volunteer writers provide invaluable reporting for the site—and in these instances HuffPo has experienced some backlash for its non-payment policy. For instance there was the case of Mayhill Fowler, the “citizen journalist” who in 2008 captured then candidate Obama’s comments at a fundraiser in San Francisco about “bitter” Americans “clinging to guns and religion.” The story generated mindboggling amounts of traffic—and therefore revenue—for HuffPo, but in fact it did more: in many ways the story became a turning point which legitimized “new media” sources, and was the beginning of sources like HuffPo and Politico getting an even seat at the table along with old giants like NY Times and ABC News.

Fowler’s compensation for role in the coup? Zero dollars. When she became dissatisfied with the chance to be a “citizen journalist,” Fowler famously quit, bitterly accusing Arianna Huffington as an “opportunist” who preyed on the talents of the willing, like herself.

It’s no small exaggeration to say that the Huffington Post has built its $315M empire on the backs of those unpaid “citizen journalists,” and in turn used it to fund the salaries of celebrity contributors like Fineman. But now that Arianna Huffington and her original investors have scored a major payday, will they be able to hold the loyalty (and content) of all those 6,000 contributors? Or will they suffer a mass exodus?

Huffington herself has said that he future of HuffPo journalism will rely more heavily on the talents of superstars like Fineman and operate less like a content farm. But as TechCrunch’s Paul Carr and Slate’s Jack Shafer almost point out, the bloggers are HuffPo’s achilles heel:

HuffPo has star contributors like Fineman and Slate has contributors like Christopher Hitchens and the occasional piece by Eliot Spitzer—if you take out all the “crap” and the mountains of search-optimized content provided by its army of “citizen journalists,” HuffPo starts to look a lot like, well…Slate.

I’m sure AOL chief Tim Armstrong and Arianna Huffington have taken this into consideration. By now most Americans are used to corporate titans making millions off their own efforts (or tax dollars) while their own salaries dwindle, so maybe HuffPo’s blogger army will just take it on the chin and keep shelling out all that content (the “crap” and non-crap alike) to keep AOL and Huffington Post in the green.

For AOL’s sake, I hope they do. 2010 was Huffington Post’s first profitable year. If the HuffPo blogger army starts to defect en masse, AOL may have just made their biggest multi-hundred-million dollar mistake since Bebo.