Terry Semel's ordeal has been so prolonged that one has to ask: why did the board choose this moment to push him upstairs? After all, in revenues, the company was overtaken by Google, its nemesis, as early as 2005. Yahoo's annus horribilis was 2006, when the stock fell in the midst of an internet advertising boom, and the Peanut Butter Memorandum signaled open revolt among the company's managers. That was Semel's most vulnerable moment: the low point of its shares, which tempted in hedge funds, less patient than Yahoo's earlier investors. So why now?After all, just last week, Kara Swisher, a close Yahoo watcher, was still arguing that Jerry Yang would never countenance the aggression of a move against the man who saved his company. One could argue that the last week's shareholder protest against the board's slate -- 33% of shares were withheld -- was the last straw. Or that the uncertainty over Semel's future was making it impossible for Yahoo to fill top management slots, two-thirds of which remain open. But the truth is that embattled chief execs are like tectonic plates. They seem as solid as the earth itself, even as the pressure builds, until, suddenly, cataclysmically, the faultline slips. And then everybody goes around saying that disaster had been inevitable.</img>


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