Who's in charge at Facebook?A tipster reports spotting Mark Zuckerberg in San Francisco today, outside 21st Amendment in San Francisco. He was "having a conversation (all smiles) with two other guys," our tipster tells us. The restaurant and bar is near San Francisco's South-of-Market startup epicenter, so there's any number of reasons Zuckerberg might have been in town. But I can think of one reason why he'd be all smiles: He's not in Palo Alto, where Facebook COO Sheryl Sandberg is busily wrecking his company. When Zuckerberg hired Sheryl Sandberg as Facebook's COO, he said she would not be in "overall charge" of the company, but would stick to running business operations. As she's repeatedly meddled in technology and product, Facebookers have asked Zuckerberg what's going on — and he's kept repeating his "overall charge" promise, even as Sandberg pulls an Al Haig — "I'm in control here" — down in Palo Alto. Zuckerberg's misdirection is entirely intentional — and very revealing of his management style.Zuckerberg tends to fall in love with his latest hire, and give that person more and more responsibility, until there's some obvious failure. Even from the outside, it's crystal clear that's what happened with Oven Van Natta, Sandberg's predecessor as COO; it happened, too, with Chamath Palihapitiya, whose portfolio waxed and waned with Zuckerberg's favor. So Sandberg's rampage through Facebook's technical ranks is just par for the course. If past experience is any indication, Zuckerberg's hanging back, keeping his fingerprints off her actions, and waiting for her to trip up. Her botched handling of ace product marketer Ben Ling's departure may be what turns Zuckerberg against Sandberg — or not. What's clear: When his disfavor arrives, it will be sharp, cold, and unmovable. Sandberg won't know what hit her. And Zuckerberg will be all smiles — like he was today in San Francisco.