The giants always have an eye on each others top hierarchies so as to counter and contrive plans to win over each other by luring and recruiting them. With advertising being the future source of revenue flooding, corporate relations do matter, which is why people at the top of the hierarchical ladder are important to be retained at the end of every quarter.
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While the chairman and managing director of FB is supported by six directors, the CEO and chairman, Larry Page and Eric Schmidt respectively are backed up by eight guys. It is obvious that crucial people like the CFO, COO are too important for the companies as it is quite difficult to find a good replacement for all the well established roles.
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Here is a chart of the top most hierarchical levels of the internet giants for a better idea.