To me it seems that when users are going to upgrade to or buy Windows 8, they will probably opt-in to cloud storage from Microsoft. Long term Microsoft may lock-in a very significant percentage of desktop, laptop, smartphone and tablet users to their services. It doesn't seem to be a level playing field for e.g. Dropbox.
More generally speaking, it looks like the big three have a strategy to use the OS as the 'gateway drug' to their online (cloud) offerings. By offering integrated always available API's to 3rd party developers they ensure the path of least resistance always leads towards iCloud, Google Docs/Drive and Windows Live/SkyDrive.
Microsoft still has a monopoly on the desktop as far as I can tell. So it's going to be interesting if another antitrust case will be started. We may end up with a 'Windows 8 N' or a "Select your cloud provider" choice screen in the future.