On the Web, it's a different story entirely. Unlike in print, Web copy flow (and the rag it creates) varies from user to user, depending on the browser, monitor resolution, and default font style and size. For this reason, you often see unsightly, deep rags resulting from narrow columns of copy containing long words, made worse by the lack of hyphenation in most Web copy. For this reason, I recommend adding a word space around dashes in Web copy to allow for more line break options.