The technology sector has been one of the fastest growing market segments in recent history. With numerous industry leaders such as Microsoft and IBM continually innovating in the space with new and improved products, technological advancements have gone from the first automatic, programmable machine in 1941, to now hand-held smartphones capable of almost any task demanded of them. While there have been many firms on the forefront of this movement, none have been more prolific in recent years than Apple [see also Apple & Verizon Team Up on iPhone: How Will ETFs Respond?].

Apple has brought to market many household names like the iMac, iPod, iPhone, and the iPad, a line of products that have taken over the industry in a number of key segments. Credited with the brilliant innovation of these numerous products is Steve Jobs, CEO of Apple (Nasdaq: AAPL). But while Jobs, recently voted CEO of the decade, has been one of the major keys to Apple's success, his health concerns have been a major roadblock in recent years. In 2004, Jobs was diagnosed with a cancerous tumor in his pancreas, forcing him to take a leave of absence. After successfully battling cancer, Jobs again took a leave of absence in 2009 to undergo a liver transplant, as his health had been deteriorating. Both of these occasions had two things in common: Jobs returned in good health to the company, and Timothy Cook was acting CEO in both cases. One of the underlying issues with these illnesses is the way in which Apple kept them under wraps, only telling investors the detail of Jobs' ailments after the fact [see also Three ETFs to Watch This Week: QQQQ, IAI, QCLN].

Yesterday, it was announced that Jobs would be taking a medical leave of absence to focus on his health. While Cook will again be acting CEO, and run the day-to-day operations, Jobs will still be involved in major decisions at the company. But with Jobs being such a pivotal part of Apple's strategy and mission, many are worried how the company will perform in his absence. As Cook will begin another stint as acting CEO of Apple, investors may have more confidence in him then previous years, as he has had a strong performance in his last showing as CEO of the tech giant. But despite Cook's bright track record, Apple shares were down approximately 7% in German trading yesterday, in light of this unfortunate news regarding one of the most famous CEOs in the world.

With U.S. markets closed yesterday, unable to react to this major news, today's ETF to watch will be the iShares Dow Jones U.S. Technology Index Fund (NYSE: IYW). IYW's top holding is Apple, which makes up over 13% of the entire ETF. This fund has had a promising start to 2011, returning over 4% thus far. Today will be a major day for IYW, as it will be reacting to Jobs' medical leave, and Apple will also be reporting earnings. Apple tends to beat the Street estimates when it comes to earnings, but a strong earnings report may still be overshadowed by the news of Jobs' illness and sudden departure. Investors who own IYW should carefully watch this fund today as it will likely be a big mover [see IYW's fundamentals here].

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Disclosure: Photo courtesy of Matt Yohe. No positions at time of writing.

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