There are very few topics with me that are untouchable for jokes. There are a few but they are very limited. I like my humor uncensored, unusual and often under the belt :)
I see no harm in a fridge magnet that says "bottoms up - it's 5 o'clock somewhere!".
We cannot lose our sense of humor in the midst of our politically correct leanings these days.
But I agree that if it's a theme throughout a house, it kind of loses it's humor. A joke is only spontaneously funny once.