I thought that this comment was interesting;
"On the other hand, automatic updates provide the possibility of foul-ups of hitherto unseen dimensions. A quickly rushed out security update with a bug in it could be automatically propagated to millions of machines. If the bug was severe enough to prevent users from downloading the fix-to-the-fix, the disruption would be massive. "
This actually happend reciently in New Zealand with the local pay phones. The tellico updated the firmware of the telephones remotely, but there was a bug in the firmware :-( The bug was so bad that they couldn't roll it back remotely and for each telephone affected (20% of all payphones in NZ) they had to send out a technician and reinstall the software manually.