As congratulations rain down on new Facebook COO Sheryl Sandberg, her predecessor, Owen Van Natta, is left under a cloud. Van Natta left Amazon.com for Facebook when it was barely out of an Ivy League dorm, and turned it into a company with plans to take over the world. Then he got demoted. Then he abruptly left. Why? Because he wanted to be a CEO someday. But his ambitions did not match his talents, Mark Zuckerberg now implies. In Zuck's words: "With bringing in a COO, we just decided it was the right time for him to go and do that." Somewhere else. Ah, then we shouldn't call it a firing.