Apple’s board promptly adopted the two recommendations he made in the brief eight-sentence letter: to name Jobs as board chairman and to "execute our succession plan and name Tim Cook as CEO of Apple." Cook has been the company's long-serving COO and has three times served as acting CEO since 2004. In each case, Jobs took a leave of absence for health reasons.

In his letter, Jobs wrote "I have always said if there ever came a day when I could no longer meet my duties and expectations as Apple's CEO, I would be the first to let you know. Unfortunately, that day has come." The vague comment is sure to re-ignite intense speculation on Jobs' health. In January of this year, to "focus on my health." Characteristically, his bare-bones, six-sentence statement then gave no details of the health issues prompting the decision.

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And neither nor even hinted at why "that day has come."