Randi Zuckerberg, the limelight-seeking sister of Facebook CEO Mark Zuckerberg, has learned a key lesson of media success: As you scale the ladder, make sure to jab your stiletto heels into the faces of those you climb over. Zuckerberg, whose day job is in Facebook's marketing department, has been writing weekly for former magazine editor Tina Brown's mostly ignored Daily Beast website since it launched — but only recently has she turned mean. We love it, of course. The target of her freshly poisoned pen: the hipster lip dub , those single-shot singalongs so popular with startups and would-be Internet celebrities. What Zuckerberg does write: "In case there was any doubt that the chief purpose of the Internet is to perpetuate narcissism, lip dub videos put that to rest." What she does not write:She has participated in many a lip-dub video herself, including one with Julia Allison, the New York party attendee who parlayed a career of writing about nothing for magazines to appearing on the cover of magazines for doing nothing. Allison is not mentioned in her piece, but she is surely present within it; Zuckerberg mentions "Flagpole Sitta," a lip dub performed by the employees of Connected Ventures, the ex-startup of Allison's ex-boyfriend Jakob Lodwick. Allison dispatched, Zuckerberg moves to targets closer to home, taking on the Camp Cyprus 20, the Internet 20somethings who filmed themselves singing along to "Don't Stop Believin'" at a seaside vacation home in Cyprus right as Wall Street imploded. What she does not mention: That the first person we see in the video is her Facebook coworker Dave Morin; Facebook engineers and designers appear later. Zuckerberg slams them all equally: "You hate them for having so much fun — damn that unbridled, financially secure joy!" Next target: Revision3, the San Francisco online-video startup best known for recording Diggnation, a podcast by Digg founder Kevin Rose. "They probably won't be recording any more lip dubs any time soon, we hear they laid off a third of their staff this week," Zuckerberg writes. Ouch! She could have added that after reading her article, Revision3 also won't be lending out its production facilities for any more of Zuckerberg's music videos, as it did for "Dontcha," a spoof about the iPhone . Ah, the smell of burnt bridges. Zuckerberg, in person, comes across as shy and self-effacing. The only hint of bile I ever detected was in a previous video, "Valleyfreude ," where she mocks Friendster, an also-ran social network crushed by Facebook, and scoffs at Yahoo for offering Facebook a mere $1 billion in an acquisition offer her brother turned down. But Randi Zuckerberg has always had her eyes on a bigger stage than the Valley. Even her job at Facebook, running the site's election-related features, has been helpful in this regard, landing her on ABC and other news broadcasts to talk about online get-out-the-vote efforts. Now she's moonlighting for Tina Brown , in the hopes of getting her hooks into New York media circles. The Daily Beast, an unwieldy, overstaffed website, is an unlikely candidate to emerge from next year's economic wreckage. But that won't matter to Zuckerberg: She's already perfected the art of stepping over those she can safely discard. Watch out, Facebookers: Do you think she'll forget how you made her take "Valleyfreude" offline?