Let's not forget that by default, Windows 8 now stores even your personal documents in the cloud. Basically everyone around the world is being directly spied upon by the NSA. We need a strong offshore tech community with real choices ASAP.
Having never used a Surface RT, I have no idea how it works there, but on the desktop Windows 8 does not force you to store anything in the cloud.
SkyDrive and the Windows Live accounts have access to your local machine as well.
This inversion from Windows 7 is not acceptable in my opinion.
What happens if you've lost internet access? (Internet outages happen!) Can you no longer log in to Windows?
If you have no Internet access (as per no domain access on Windows), it uses cached credentials.
It seems convenient on the surface but I can think of many ways it's a really, really bad idea: third party snooping, the possibility of being locked out of your own computer if your Microsoft account is deleted/deactivated/password changed, possible expiration of cached credentials (and therefore inability to log in) during a protracted period of internet unavailability, etc
For the majority of users, they will miss the tiny text at the bottom which allows local accounts an will be put off by the big warning about how crappy local accounts are immediately afterwards.
The result is a big conversion to Windows authentication being moved to "The Cloud" and therefore under the eyes of every nefarious agency out there.