The problem is that if you are locked in with a choice of 100% Microsoft or 0% Microsoft, once someone goes, it isn’t a baby step, they are gone. Once you start using Google Docs and the related suites, you have no need for Office. That means you, or likely your company, saves several hundred dollars a head. No need for Office means no need for Exchange. No need for Exchange means no need for Windows Server. No need for Office means no need for Windows. Once the snowball starts rolling, it picks up speed a frightening pace.
For me, the shift away from Microsoft happened one app/device at a time.
I gave up Hotmail/Outlook for Gmail. Windows Media for iTunes. Windows Photoshop for Mac Photoshop. Downgraded from a Pocket PC to an iPod, which eventually upgraded to an iPhone. And then an iPad.
It all just snowballed from there. And clearly an entire market has been experiencing the same thing too.