You folks don't get it. If the service sucks, why should I not reduce the tip? If you go out to eat and the waiter stinks, do you still leave 15 - 20%? If you do you are not doing the waiter or the establishment any favors.
Poor service should be brought to management's attention so it can be fixed.
And no, I have NEVER reduced my tips on a cruise. I always give them more cash. Now, I have had a problem with the wait staff on one cruise. I talked to the manager and he spoke to the wait staff. Things got better right away.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08