After less than 10 months on the job, MySpace CEO Owen Van Natta has resigned, leaving the Rupert Murdoch-owned social network once again headless.

MySpace is already in a heap of trouble. In December, MySpace attracted 70 million visitors, down from 78 million in the year-earlier period. And its under-performing ad deal with Google, once valued at $900 million, is due to lapse later this year. Van Natta, hired away from Facebook where he was its COO and CRO (dotcom-speak for Chief Revenue Officer), clearly didn’t manage.

One of the reasons for MySpace’s decline may be that its users are not such a great match with advertisers. In her controversial essay “Viewing American class distinctions through Facebook and MySpace,” media scholar Danah Boyd describes MySpace users as “still home for Latino/Hispanic teens, immigrant teens, ‘burnouts,’ ‘alternative kids,’ ‘art fags,’ punks, emos, goths, gangstas, queer kids, and other kids who didn’t play into the dominant high school popularity paradigm. These are kids whose parents didn’t go to college, who are expected to get a job when they finish high school.”

Facebook users, on the other hand, “come from families who emphasize education and going to college. They are part of what we’d call hegemonic society,” according to Boyd.

Since the publication of this 2007 essay, the fortunes of Facebook and MySpace have diverged even further.

No doubt, Murdoch’s New Corp. can read the writing on the wall. They now intend to convert MySpace into a portal that guides users to movies, music, TV shows and games – in other words, some of Murdoch’s old media properties.

What does all this mean for other social networks struggling against Facebook’s hegemony? Some are finding geographic niches, such as Orkut’s success in Brazil. Others, like China’s QQ and Russia’s V Kontakte rely on linguistic barriers. Meanwhile, MySpace faces the toughest task of all: competing in Facebook’s backyard with a mess at the top.