There is a good article in the current edition of Conde Nast Traveler about the piracy incident. The article says assaults on passenger vessels isn't something to get overwrought about. Cargo ships and yachts are the primary targets. It may be that this bunch of hoseheads thought the Spirit was a private yacht, albeit a large one. The pirates do a brisk business re-selling yachts, and with stolen cargo. Passenger ships have too many negatives - crowd control, large crews with trained security officers, etc.