As we've discussed here before, much of this is Microsoft's long term strategy of building a consistent ecosystem through a range of products.
Similar to Google, Microsoft’s pooling a strategy around its existing products, from game consoles to office software. And similar to Apple’s strategy, Microsoft is streamlining its OS around a narrow device lineup, connecting everything in the cloud. The payoff is already predicted to hit in 2016, when IDC expects Windows Phone to overtake Apple iOS as the second-most dominant mobile platform in the market. And taking a look at some recent developments from Microsoft, IDC’s prediction may be onto something.
SkyDrive is one of the ways Microsoft is joining its ecosystem together.