A 23-year veteran of Microsoft, was revealed in a memo by company CEO Steve Ballmer on Monday. "Bob Muglia and I have been talking about the overall business and what is needed to accelerate our growth. In this context, I have decided that now is the time to put new leadership in place at STB," said Ballmer, who nonetheless in the STB business.

Analysts speculated on a range of causes for the shakeup.  "I think in some ways it's based on some frustration that maybe they're not moving as fast to the cloud as Microsoft would like," said analyst Jeffrey Hammond, of Forrester. Although the company's Windows Azure platform is progressing nicely, it may not be making the kind of headway Microsoft sees with rival Amazon's EC2 (Elastic Compute Cloud), said Hammond.

There also could be frustration with last fall's confusion over the rich Internet application plugin platform, in which Muglia spoke of a new direction for Silverlight. That resulted in confusion over whether Microsoft was still committed to Silverlight. "That was kind of a gaffe that caused a lot of problems for Microsoft. I think they've recovered," said Hammond.

Microsoft declined to provide comment beyond Ballmer's memo, which did emphasize the company's moving into "the new era of cloud computing