SAN FRANCISCO (Business 2.0) -- It hasn't been a good month for Microsoft's Google-fighters. So bad that one left abruptly last week, and another decided this week to switch teams.

Vic Gundotra, a general manager for platform evangelism at Microsoft and a 15-year employee, has agreed to join Google after first spending a year working on charitable endeavors, Business 2.0 has learned.

"Mr. Gundotra has resigned from Microsoft (Charts) and entered into an agreement with Google," Google (Charts) spokesman Steve Langdon wrote in an emailed statement. "He will not be a Google employee for one year and intends to spend that time on philanthropic pursuits. We are uncertain what precise role he will play when he begins working for Google, but he has a broad range of skills and experience which we believe will be valuable to Google."

Microsoft spokesman Tom Pilla confirmed Gundotra's departure and says that the executive has a noncompete agreement with Microsoft preventing him from working for a competitor for one year after leaving the company.

Gundotra had been charged with getting developers to write programs that build on top of Microsoft's desktop software and online services. Most recently he had been working out a strategy to compete with the draw of Google's newer, Web-based software applications.

His departure comes shortly after the abrupt departure of Martin Taylor, a corporate vice president charged countering Google by marketing Microsoft's Windows Live and MSN services.

Taylor ranked higher than Gundotra, but Gundotra's role at Microsoft may have been more critical than Taylor's marketing work. In technology, "evangelism" - which was Gundotra's main duty - is the process of reaching out to independent developers and persuading them to use that company's products as a platform upon which to write software programs.

Microsoft CEO Steve Ballmer gained infamy when a video clip of him chanting "Developers, developers, developers," at a company event spread around the Internet. But although Ballmer may have looked foolish, the courting of developers is a deadly serious matter for Microsoft.

"Evangelism is a significant part of Microsoft's success, and Vic has been a key part of that," says Greg DeMichillie, a senior analyst at research firm Directions on Microsoft.

Over the past few years, Gundotra has led an effort to reach out to software developers through blogs, online video, and other Web-based tools to present a friendlier face. He hired Microsoft blogger Robert Scoble, who became perhaps the best-known corporate blogger around. Scoble is now leaving the company as well.

As a result, "overall, developers are much more satisfied with Microsoft than they were three or four years ago," says DeMichillie.

But Microsoft faces a threat from Google that goes beyond trouncing MSN in the Web search business.

In Google, software companies see an example of a different way to write software and make money off of it. Google has popularized technologies like Linux and Ajax that compete with Microsoft Windows as tools for writing code, and shown that companies can make money off of Web-based software that is supported by online ads instead of by selling packaged software designed to run on desktop operating systems like Microsoft Windows.

Google also has started to create a software platform of its own, allowing developers to create new Web-based software based on services like Google Maps, Google Earth, Gmail and its AdWords advertising service.

Gundotra had been leading an effort to persuade developers to build software on top of Microsoft's MSN and Windows Live online services instead of Google's platform.

His departure will hardly hamstring Microsoft, a company with 70,000 employees. But Gundotra's move to Google is the latest in what has to be a disturbing trend to Microsoft's top management.

Among the ex-Microsoft executives and top technical talent now at Google are former Microsoft China head Kai-Fu Lee; Mark Lucovsky, a top engineer whose departure upset Ballmer so much that the CEO allegedly threw a chair across an office; and Adam Bosworth, a former general manager and software expert.

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