After Steve Jobs, who will run Apple?

But it's hard to argue that Cook has become Apple's go-to-guy. "The next six months are going to be basically a trial period for Tim Cook to be CEO," argued Brian Marshall at Broadpoint Amtech, in an interview with Reuters. "If that period goes well, my expectation is that Steve will pass the baton over to Tim in June and basically Steve will be his senior adviser."

Looking in or looking out?

If Apple doesn't pick Cook as its next chief executive, then who else is there? In theory, Apple could do what many major firms have, and look externally for a new leader.

But analysts seem to agree that Apple's next chief will come from the ranks. McGuire suggested an internal candidate or possibly a former Apple staffer who has proved their merit externally as the most likely option. "The company's no longer just a computer hardware and software company," he suggested. "They've reinvented, or at least reinvigorated, important parts of the consumer-electronics market, so bringing some outsider in with perhaps some experience in one or two of those businesses might not be enough. Having some familiarity with core aspects of Apple's business is going to be important," he added.

The next Apple leader is likely to be internal, agreed Quocirca's Longbottom. "It's likely to be internal for a period of time at least. The problem is that Apple has to be very careful where they go if outside," he said.

Internally, Cook does seem the strongest option. Longbottom suggested Jonathan Ive, Apple's senior vice president of industrial design, and the lead on such projects as the iMac, iPod and iPhone. But the analyst added: "He's a quiet guy who I think is happier in the design labs than in the political limelight of an operational role."

Other than Ive, Longbottom said: "No one else springs to mind...."

Aside from Ive and Cook, Jobs himself mooted chief financial officer Peter Oppenheimer as a possibility, at a shareholder meeting in March last year, saying: "We've got great talent, and I think the board would have really great choices."

Does the end of Jobs mean the end of Apple?

But if there is so much potential inside the company, why do the markets panic so much everytime Jobs loses weight?

McGuire suggested Jobs is just too important to the firm but making him the focus of Apple was a move they needed to take. "Establishing Jobs as the spokesman for the company was absolutely essential back in 1997 because his full-time devotion to the company was required to establish credibility. Not just to investors, but to developers, potential employees, et cetera. The tradeoff of that strategy? What we're seeing today," McGuire said.