Microsoft makes it easier for 3rd party devs to add Windows Live features to apps
As part of Microsoft's updated developer platform, devs will now be able to hook their apps into Windows Live, Hotmail, Messenger and Skydrive to allow users access and control over their content. Microsoft has actually made it incredibly easy for developers, so there will be no need for server-side code, because Microsoft says that many app devs don't have servers backing their apps. Microsoft wanted to add light and easy access to content in an effort to bring a social layer to WP7 apps using the networks that Microsoft has been building for years in Hotmail and Messenger.
The new features even allow for offline access to user data, but early comments say that there is a bug in that system because the authorization tokens expire after just one hour. It seems likely that Microsoft will fix this issue fairly quickly. But, we can't wait to see how devs put this new functionality to use.
source: Windows Team Blog