I have frequently been asked for ID and/or ship card to enter the port area We surrendered our passports to the purser when passing between Greece and Turkey. Sure enough when we got them back they had been stamped in both countries. But we didn't have to carry them with us.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Alaska 2014 - haven't picked a cruise yet
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, Caribbean 2013