They don't seem to have created a way of completely disabling SkyDrive using a GPO (Group Policy Object)!

http://social.technet.microsoft.com/Forums/office/en-US/0e84...

NB woe provided a correction to this - I (perhaps understandably) confused this feature with SkyDrive for Office, which appears to be something different...

[NB woe's comment is dead, for no obvious reason]