Facebook CEO Mark Zuckerberg appears to have been outed as not caring one whit about your privacy — a jarring admission, considering how much of our personal data Facebook owns, not to mention its plans to become the web’s central repository for our preferences and predilections.

Also interesting is how this came about: Not in a proper article, but in a tweet by Nick Bilton, lead technology blogger for the The New York Times‘ Bits Blog, based on a conversation he says was “off the record” and which he may have confused with “not for attribution.”

“Off record chat w/ Facebook employee,” begins Bilton’s fateful tweet. “Me: How does Zuck feel about privacy? Response: [laughter] He doesn’t believe in it.”

Ouch.

Zuckerberg’s apparent disregard for your privacy is probably not reason enough to delete your Facebook account. But we wouldn’t recommend posting anything there that you wouldn’t want marketers, legal authorities, governments (or your mother) to see, especially as Facebook continues to push more and more of users’ information public and even into the hands of other companies, leaving the onus on users to figure out its Rubik’s Cube-esque privacy controls.

Facebook has been on a relentless request over the past six months to become the center of identity and connections online. The site unilaterally decided last December that much of a user’s profile information, including the names of all their friends and the things they were “fans” of, would be public information — no exceptions or opt-outs allowed.

Zuckerberg defended the change — largely intended to keep up with the publicness of Twitter, saying that people’s notions of privacy were changing. He took no responsibility for being the one to drag many Facebook users into the net’s public sphere.

Then last week at its f8 conference, Facebook announced it was sending user profile information in bulk to companies like Yelp, Pandora and Microsoft. Thus, when users show up at those sites while logged in to Facebook, they see personalized versions of the those services (unless the user opts out of each site, somewhere deep in the bowels of Facebook’s privacy control center). On Tuesday, four Senators asked the company to only push data to third-parties if users agree to it, a so-called “opt-in” that social networking sites like Facebook, Twitter and Google Buzz eschew since it radically cuts down on participation and thus revenues.

Facebook is also pushing a “Like” button, which lets sites put little Facebook buttons on anything from blog entries to T-shirts in web stores.

Clicking that button sends that information to Facebook, which publishes it as part of what it calls the Open Graph, linking your identity to things you choose online. That information, in turn, is shared with whatever sites Facebook chooses to share it with — and to the sites you’ve allowed to access your profile.

It’s an ambitious attempt to rewrite the web as a socially linked network. But many see Facebook’s move as trying to colonize the rest of the web, and keep all this valuable information in its data silos, in order to become a force on the web that rivals Google.

So it’s no laughing matter that the head of Facebook appears not to care about privacy. (We asked Facebook to clarify Zuckerberg’s privacy stance but have yet to hear back.)

For his part, Bilton fired off a number of salvos defending his understanding of the the ground rules which governed the conversation he had. “‘Off record’ means there is no attribution to who it is but conversation can be used in story. ‘On background’ means I can not repeat it,” wrote Bilton. He took over the Times‘ technology blog in the last few months, after a long stint working with its technology-development team.

Unfortunately, he’s wrong about the definitions.

“‘Off the record’ restricts the reporter from using the information the source is about to deliver,” reads NYU’s Journalism Handbook, in one definition of the phrase. “If the reporter can confirm the information with another source who doesn’t insist on speaking off the record (whether that means he agreed to talking on the record, on background, or not for attribution), he can publish it.” “On background” usually means that information can be used, but can’t be attributed to a specific person.

Bilton later responded to our request for clarification, saying, “My source said it was OK to quote them, just not say who they are.” So apparently, this Facebook employee wanted this information to get out, for whatever reason.

Now, the die has been cast: The world knows that a Facebook employee thinks his CEO “doesn’t believe in” privacy, which should scare the bejesus out of anyone with a Facebook account — and that encompasses just about everyone reading this now.