First, a disclaimer, just in case you weren't sure: I'm not Steve Jobs's doctor. And I believe that all of us who aren't responsible for his medical well-being are in no position to have an informed opinion about it--and that to deal in rumor on the topic is just plain rude. (Even the most famous CEO on the planet is entitled to some privacy.) So I'm not going to make any guesses about the present or future of the man's health. Or say much of anything about it other than that I wish him a full and speedy recovery from the issues that so many people have speculated about in such detail based on so little hard information.
But with Jobs' announcement yesterday that he plans to go on medical leave until the end of June, one thing is fact, not conjecture: Assuming that Jobs' leave of absence is no shorter or longer than he expects it to be, Apple will spend slightly under half a year without the day-to-day involvement of its cofounder and CEO. That would be a major deal for any company. For an organization as symbiotic with its leader as this one, it's extraordinary. (When Bill Gates announced he was abandoning day-to-day involvement in running Microsoft, not for half a year but forever, it was major news; nobody, however, questioned Microsoft's viability or even expected it to be a very different place without him.)
So what impact will Steve's temporary removal from his company have on it? His two past extended absences from Apple over the past 33 years can't tell us too much about the next six months. The one that began in 1985 with his unwilling exodus and lasted until Apple acquired his NeXT startup in 1996 was far too long and traumatic to be comparable, and the one forced by his cancer surgery in 2004 was too short. (That second time, Jobs spent only a month out of commission and a month working part-time before returning to full duty.)
The one piece of encouraging news is that his hand-picked lieutenants are a talented bunch with deep exposure to the mind of Jobs: executives like Chief Operating Officer Tim Cook (who will run Apple in the interim), marketing head Phil Schiller, design superstar Jonathan Ive, and iPod software leader Scott Forstall. I have a hunch that pundits who are confident that Steve Jobs makes every major decision at Apple through brilliant, imperious fiat have been known to credit him with moves made by other Apple employees, and that the company's leadership will manage to make plenty of smart choices over the six months without him.
Still, no matter how competently Jobs's team soldiers on without him, he leaves a gaping hole, even if it's not permanent. When you think of new Apple products, you instinctively envision Jobs onstage at a Stevenote, engaging in the one-man hooplafest that gives even mundane offerings an incalculable boost. It's a safe bet that the company will announce something--multiple somethings, actually--during his absence. But Steve Jobs keynotes come and go, and sometimes they don't happen at all, even before the advent of the Phil Schiller Macworld Expo keynote. The most popular Mac of all time is the MacBook; the first one was announced with a press release, not a Jobs appearance.