Vic Gundotra, GM of Platform Evangelism, is leaving Microsoft.

CNN announced it yesterday. It's also being talked about in Robert Scobble blog post.

Should we consider Microsoft is undergoing a brain drain as is being said in CNN's article?

No, I don't think so! In a company our size, it's simply inevitable that people leave ... as others come in. It's just that those who come in are not much talked about!