It turns out it was more like a misunderstanding that spiraled out of control.
One of the Anonymous members affiliated with the original plans for an "Operation Facebook" laid it all out on Pastebin, a text-uploading app, explaining how an abandoned online chat room devoted to protesting Facebook's porous privacy controls snowballed into a virtual death threat:
The plan before it was scrapped had been a mass deletion of facebook accounts ... it was decided that a mass deletion of facebook accounts would occur on november the 5th, however this was decided to be a bad idea and so it was removed from the pad. Unfortunately, this left only the draft of a message to facebook, warning that they would 'never forget' the 5th of november. At some point, somebody saw the near-empty channel and joined it. Rumours were spread ranging from 0-day exploits in facebook to physical attacks on the server. Soon #opfacebook gained around 40 people who expected an attack on facebook.
Then someone created an ominous video and uploaded it to YouTube in mid-July, the media caught on a few weeks later, and before you knew it, we were all bracing for the destruction of the gargantuan social networking hub come fall.
Gawker's Adrien Chen spoke with the Anonymous member who posted the explanation of what had really happened. "An attack on Facebook would be ridiculous," the member said. "Even if it succeeded, Facebook has a lot of users, and we want to help people, not hurt them."
Nevertheless, Chen reports: "After the frenzy of news reports and blog posts, the old Operation Facebook room is filled with more people than ever. Only now they're tossing around outlandish ideas for attacking Facebook and its users, instead of planning a 'peaceful' protest. Operation Facebook might be back—for real, this time."