I remember reading a review in which the reviewers mother was not allowed to board an Alaska cruise because she was from Mexico and did not have the proper documents to enter Canada. I recall the person being extremely terse with the cruise line for not informing him/her about this requirement. Being objective, my first thought was that the cruise line cannot possibly alert every passenger of their specific visa requirements. Then I thought... well they do inform passengers to check for themselves... so clearly someone dropped the ball on the "checking for themselves" part. In any event, I felt bad enough about it to post about this site (applies to US travelers).
Do you check Visa requirements, vaccination/inoculation requirements, etc. prior to your traveling out of your home country?