From [url]http://oradoc.photo.net/ora816/paraserv.816/a76970/psadm_ba.htm[/url]
Warning:
Do not use operating-system utilities to back up the control file in ARCHIVELOG mode unless you are performing a closed, whole backup.

Since the document doesn't specify the issues of such an action, could someone explain what types of problems this would cause?

Thanks,
Mark