One December a few years back, I was in Santa Claus, Indiana, and went to the Post Office - a popular destination thanks to its seasonal postmark. "Merry Christmas!" I said provocatively. But Postmistress Sandy Colyon was ready for me. "A week ago," she said, "I'd have had to say 'Happy Holidays', but we've been given a special dispensation from the Postmaster-General allowing us to say 'Merry Christmas'. So Merry Christmas!" That's "Christmas" at the dawn of the third millennium - a word you have to get a special memo from head office authorising the use thereof. In America, most...