I think a better title for your post would be "If you want a nightmare, cruise in hurricane season".
Yes, I'm sure I would be very disappointed if I planned and researched ports for months in advance, had the perfect excursions planned and then found that we couldn't make it and had to stay onboard the ship for those days. But sometimes safety has to come first. It's been said that other ships were able to make it to different ports - I'm sure each port can only hold so many ships. As another poster said, Carnival shoud have split the ports up between their ships instead of having one ship get three ports and another only one - that would've been the fair thing to do, but they didn't do that for whatever reason - maybe there are reasons why it couldn't be done - we don't know.
The best way to ensure this doesn't happen, although it still can for other weather related issues but less often, is don't cruise during hurricane season - you sometimes get what you pay for - hence the cheaper fares! I would never consider going to Florida or any Caribbean island for a land vacation during hurricane season, let alone on a cruise ship!