Like anchovies, olives are another controversial pizza topping. Some people can't stand them. Other people love them -- whether they're green, black, Greek, marinated or stuffed. Olives can be oily, salty, sour and bitter, which, for some people, makes them difficult to stomach.
Why do we dislike bitter flavors? Well, we're actually genetically programmed to have a negative reaction to bitter tastes to protect ourselves. Many times a bitter taste indicates something is poisonous or otherwise dangerous to our bodies. So when we decide we "like" something that tastes bitter, like the flesh of an olive, we're ignoring that warning signal in order to enjoy the olive for its other flavors.