No matter how well Carnival handles the passengers in refunds, etc., they still have 4000 people that will be telling that story to at least 10 people of how bad it was. This is basic customer service math so now there are 44,000 people strongly biased against choosing Carnival for a cruise or even going on a cruise at all.
I'm thinking more like everybody who reads about this debacle will (a) never consider going on a cruise with Carnival or whatever they change their name to next week, and (b) be strongly disinclined to go on any cruise, ever.
I've never been on a cruise but have wanted to go on one of the Alaska cruises one day but now I'm not too sure.