If you think that DRM that locks you out of a song or movie that you've bought is bad, imagine being locked of document that you created, and being able to do nothing about it until a patch is released.
This is exactly what happened to Microsoft Office 2003 users who had protected their documents using the Rights Management Service (RMS) feature. Starting on December 11th, users trying to open documents protected by RMS were greeted by the following error message:
"Unexpected error occurred. Please try again later or contact your system administrator"
The problem, it seemed, was down to an expired security certificate. There is a hotfix available.
It is, however, a cautionary tale. The fact that Microsoft didn't update this certificate in a timely fashion is an indication that Microsoft wasn't taking this feature a seriously as some of its customers were.