A friend of my mother's were on a cruise when her husband got sick. It was Costa Rica I think but might have been Dominican Republic...in any case, the hospital had no ac and nuns running the wards. They had netting at the windows to 8out the bugs but he was still covered in mosiquito bites. The ship just dropped them off with no assitance (not even help her find a hotel in a country where she was unable to speak the language)
A similiar situation happened to my husband. However the Carnival doctor was great. We were leaving Cozumel when he had terrible abdominal pain. We were heading back to Tampa and the doctor wanted to keep him onboard long enough that we were closer to America soil. It seems if they airlift you off of the ship it's $15000 cash up front (can't imagine what you would do if you didn't have that kind of money since the ship is kicking you off) and they take you to the closest point of land, not the country you request.
Just little things that make you realize that you although I love cruise vacations and the majority go off without a hitch (although I was on the nightmare transatlantic crossing of MSC Orchestra in 2009) you are at the mercy of the cruiseline and had better saved up plenty of back up money just in case.