In theory it should not happen, but in practice it occurs over and over: a particular package from Ubuntu's archives causes undo problems for many Ubuntu users. One example was in 2006 when an update disturbed the X server and left many users with a black screen after a reboot.

On the ubuntu-devel mailing list, Ubuntu's Robbie Williamson announced that he would taking measures to deal with such situations more effectively. The Twitter and Identi.ca microblogging services will handle through users subscribing to one of the following accounts:

http://identi.ca/ubuntustatus
http://twitter.com/ubuntustatus

The feeds will return an alert in case of a update problem. It will at least keep users from carrying through with the update until the issue has been fixed.

The effectiveness of the alert system will prove itself in practice, because its success depends on (a) how many Ubuntu users subscribe to Twitter or Identi.ca and (b) how many will subscribe to the feed. Better yet is for Ubuntu developers to thoroughly test updates to prevent the issues in the first place.