Windows or Web? Platform wars evolve.
The way I see it is that Microsoft is trying to attract devs to the Windows 8 platform which is going to span desktop, tablets and phones. Their promise is that you can code once and run on all Windows devices.
Google is betting on the web. Gmail, Calendar and Voice are all cloud based. They are hoping to attract devs to build on the web. HTML5 websites and web apps increase the adoption of Android and Chrome OS as a daily driver.
IMO I think the Windows 8 strategy is going to fail. The web is the future. Cars, toasters and house lights are more likely to have internet connectivity rather than a full fledged Windows OS. If Android's current adoption continues to accelerate as they start to implement it into appliances, vehicles and devices than the web of things is going to explode. The next billion computers are more likely to be "smart" devices and not traditional pcs.