In Windows Vista and Windows Server 2008, if you go to a the advanced security settings for a directory and uncheck "include inheritable permissions from this object's parent", then go back to the Sharing tab, you'll find that the "Share" button is disabled. Why is this? We don't see this behavior on Windows 7 or Windows Server 2008 R2.
(Yes, a customer actually noticed and asked the question.)
The sharing wizard in Windows Vista and Windows Server 2008 does not support folders with the
SE_ security descriptor control bit because it isn't sure that it can restore the ACL afterward.
And as the customer noted, this restriction was lifted in Windows 7 and Windows Server 2008 R2.