Microsoft and any other large corporation faces challenges from outside competitors and from within when key personnel leave the company. Microsoft has been hit with key personnel defections over the last few years that have seen some of the most important managers and executives leave Redmond.

The latest top executive to leave Microsoft is Bob Muglia, who will continue to run the company’s Server and Tools Business division until the summer. Microsoft will be looking at current workers and outside Microsoft to find a replacement for Muglia, a 23-year Microsoft veteran.

CEO Steve Ballmer wrote in an email to Microsoft employees, "This is simply recognition that all businesses go through cycles and need new and different talent to manage through those cycles. Bob has been a phenomenal partner throughout this process, and he and his leadership team have the right strategy in place."

The Seattle Times reports that Muglia stepping down was a surprise to some observers. The division that Muglia runs is doing well and has grown continually into a $14.9 billion/year business and in 2010 the division generated $5.5 billion in operating profit.

Muglia sent an email to his employees stating, "The foundation of who I am is based on living with integrity. Integrity requires principles, and my primary principle is to focus on doing the right thing, as best I can. The best thing, to the best of my ability, for our customers, our products, our shareholders, and of course, our people.”

Muglia is the most recent high profile Microsoft defection. Steven Elop left Microsoft to become the CEO of Nokia last September. Chris Liddell left his spot as CFO in 2009, and Ray Ozzie left in October and wasn't replaced.

Rob Horwitz of Directions on Microsoft said, "It [Muglia leaving] did surprise me. He really did grow the third child — the first is, of course, Windows, and Office is the second child. This is one of the three really successful moneymaking businesses growing in low double digits every single year against some stiff competition like Oracle."