We all hope Apple chief executive Steve Jobs is able to overcome his obviously serious health problems and return to the job he so clearly loves. Jobs's passion for personal technology and what it can do for people -- not to mention his brilliance as an entrepreneur and tech visionary -- continues to be impressive and inspiring. (Also see: Apple don't need no stinking CEO succession plan) But two medical leaves of absence in two years for a man who had a pancreatic tumor removed in 2004 and who received a liver transplant in April 2009 has to make you worry. And if it hasn't prompted Apple's board of directors to get serious about a succession plan, then the board is being incredibly irresponsible to shareholders. Jobs on Monday sent the following email to Apple employees: Team, At my request, the board of directors has granted me a medical leave of absence so I can focus on my health. I will continue as CEO and be involved in major strategic decisions for the company. I have asked Tim Cook to be responsible for all of Apple’s day to day operations. I have great confidence that Tim and the rest of the executive management team will do a terrific job executing the exciting plans we have in place for 2011. I love Apple so much and hope to be back as soon as I can. In the meantime, my family and I would deeply appreciate respect for our privacy. Steve Jobs was diagnosed with pancreatic cancer in 2004, undergoing surgery that July to successfully have a tumor removed. On Jan. 14, 2009 -- almost two years ago to the day -- Jobs notified Apple employees that he was taking a six-month medical leave of absence to focus on his health. During both previous medical leaves, Cook, Apple's long-time chief operating officer, acted as interim CEO. However, unlike the medical leave in 2009, there was no fixed time limit for Jobs's return mentioned in today's email to Apple employees. Is that significant? It's hard to say, but the difference is undeniable. Only Jobs, his family and his doctors know for certain the scope of the Apple CEO's health issues and prognosis. Maybe the board knows too. One would hope, at least. And if it doesn't -- for whatever reason -- the board's responsibility is to assume the worst and have a succession plan in place. Maybe that succession plan is Tim Cook. In 2004, 2009 and now, Cook is the guy to whom Apple turned when it needed someone to man the helm while Jobs recovered. Perhaps he's the obvious choice to replace Jobs permanently, if it comes to that. But all that is for the Apple board to determine. It's their job. My job -- as much as I dislike it, to be honest -- is to write about the business implications for the largest technology company in the world of its CEO's obviously serious health issues. So I have. Now I'm going back to hoping and wishing that Jobs makes a full recovery.
Chris Nerney writes about the business side of technology market strategies and trends, legal issues, leadership changes, mergers, venture capital, IPOs and technology stocks. Follow him on Twitter @ChrisNerney.