Layers.com has a nice little article that sums up the problems that the dash and its variants present to the average writer and web folk.
After quotation marks, dashes are the most abused characters in the typographic stable. Dashes have visual, typographical roles as well as grammatical ones. These modest characters fall under the sway of both copy editors and typesetters, and using them correctly depends on knowing a bit of both disciplines. By the end of this article, you’ll be a bona fide dashmeister.
