Tom Rizzo, the man who basically invented Microsoft’s strategy for the Office 365 cloud productivity suite, is leaving Redmond behind after 17 years with the company in favor of a new position with Amazon Web Services.

A hat tip to Geekwire, which noticed the update on Rizzo’s LinkedIn profile. That profile update indicates that he now works at Amazon Web Services as of June 2012, working in the Amazon EC2 business as a general manager. His profuile says he is hiring.

“Tom Rizzo brought a considerable amount of energy and passion to the teams he’s been a part of during his seventeen year career at Microsoft.  We wish Tom the very best in his future endeavors and thank him for the contributions he’s made to our business,” a Microsoft representative told Geekwire.

Rizzo’s departure comes at a tipping point for Microsoft. With the unveiling of the new Microsoft Surface tablet product line, it seems pretty clear that the play here is to leverage the Office brand and build cachet with the enterprise – an idea that the competition at Google is taking to heart with its Chromebook strategy. And something we hear over and over again from vendors across sectors is the idea that the cloud is the engine that builds momentum for mobility.

We still haven’t heard much (if anything at all) about how Microsoft Office 365 might play nicely with Microsoft Surface or the forthcoming Microsoft Windows Phone 8. But Rizzo was with Microsoft Online Services as the BPOS suite transitioned into Microsoft Office 365, and he’s been the public face of and evangelist for the company’s cloud productivity vision. He could be especially relied on to talk trash about Google Apps and its enterprise readiness (or purported lack thereof). As Microsoft deepens its mobility play, Rizzo could have helped make the sell for its enterprise cloud services.

But at the same time, Rizzo liked to talk up the ecosystem of partners and service providers around Microsoft Office 365. With Amazon CTO Werner Vogels using his time on stage here at the GigaOM Structure event in San Francisco to give props to the developer community that’s sprung up around Amazon Web Services, that community mindedness might well take Rizzo and Amazon EC2 a long way together.