Last Saturday, a young man in Karachi, Pakistan, greeted a young woman in a university classroom with "Happy Valentine's Day." In most of the world these would be innocuous good wishes; in Karachi, they were fighting words. Other students objected to them, leading to a fist fight and the injury of two students. As this incident suggests, in some cultures Valentine's Day prompts controversy. The Saudi religious authorities issued an edict indicating that "There are only two holidays in Islam - Eid al-Fitr and Eid al-Adha - and any other holidays ... are inventions which Muslims are banned from" and...