Or you know, place the ability to disable Windows Update behind policy restrictions and UAC rather than being openly editable in the registry? With policy restrictions, corporate installations could deny all attempts to disable the service. In non-corporate environments, this should at least require a UAC prompt. While too many users would likely click through without understanding, at least knowledgeable users would understand and be able to deny the change.

Windows Update is a serious security requirement for any Windows install. Disabling it should clearly require explicit consent from the user.