Karen,
I had a cruise booked for next month on Seabourn. I booked it because it overnighted in Bali. In October, Seabourn cancelled all the stops in Indonesia a couple of days after the latest bombing in Bali. I called them up and pointed out that RSSC was stopping there the following week. To no avail. They reserve the right to change the ports at any time, for any reason. They refunded me my deposit but did not reimburse me for my out of pocket expenses. DH and I had to pay $200 each to change our airline tickets to go to Europe instead in May.
I do think the cruise lines constantly evaluate risk and change their itineraries accordingly.