Why are Microsoft Hotfixes password protected?
My guess would be to minimize Web distribution so that the hot fixes aren't applied to machines where they're not supposed to be.
I would guess tha the reason Microsoft hotfixes are password protected is to guarantee that you have read the EULA and it provides Microsoft with a record that you have agreed to the fact that should this patch blow up your system you are doing it at your own risk. All of the passwor dprotected hotfixes have not been mainstreamed and many times are written to address 1 specific issue.
For the most part you have to pay for hotfixes with a valid support contract (or a one-off indecent fee). I would agree with gravyface except it would be more so that you have to pay MS for the ability to use the hotfix in addtion to the being applied to machines that they aren't ment to be applied part he mentioned.