I like auto tips. My first cruises were before auto tips and I found it to be a pain to get the right change and the envelopes. Plus you have to know the standard tip amounts for each service person. With auto tipping I know the people will get the right tip without any effort from me. I also can get envelopes and leave an extra tip if I feel the service was really excellent.
I understand why some people like the envelopes they know for certain the person is recieving the tip. They feel the service is better if the tip is a cash tip at the end of the cruise (in my experience I have not noticed a difference in service). I think Carnival's style may be confusing at times, but it allows for both styles of tipping. I can leave my auto tip and you can remove your auto tip and tip in cash. I agree remove the auto tip on the last night so the staff doesn't find out a head of time and think you are going to stiff them.
In the case of this original post the Splendor was unable to go to Mexico because of the swine flu. So the ship only went to San Francisco (not a beach port). A lot of passengers were upset and felt they deserved a refund or partial refund. When one wasn't provided on the cruise (because the decision is made by the corporate headquarters) the passengers removed thier auto tips. The corporation did later provide a partial refund or future cruise credit; I can't remember which it was. The cruise ship workers got punished not because of bad service, but because the passengers felt cheated by Carnival. That was just wrong. Had I been on this cruise I would have tipped the staff normally and taken up any issues I had with Carnival directly.