According to my informant, there is a long-running superstition in theatre surrounding the name “MacBeth.” If you are in a theatre or involved in a theatrical production, you are not supposed to say the name “MacBeth” or quote lines from the play. Instead of saying “MacBeth” you are supposed to say “That Scottish Show” or something along those lines. It is akin to stepping on a crack or spilling salt; it is bad luck all around. She says that if you say “MacBeth” around a theatre or while you are working on a play, then the theatre will burn down or someone will die on stage. It’s just something you are not supposed to do. My informant learned this from her high school theatre teacher. Someone in rehearsal had said “MacBeth” and the teacher went pale and screamed at this offending student to leave the room and wash out her tongue or something.
After researching on Wikipedia and other websites, I have discovered that the taboo against saying “MacBeth” has many supposed origins. Some believe it is because the original globe theatre burned down after a production of MacBeth, others believe it is because a real sword was accidentally used instead of a prop sword, and someone was killed during a performance. Others still think it comes from the fact that the witchcraft lines used in the play are real magic, thus cursing each and every performance. Some believe that Shakespeare stole these lines from an actual witching coven, and these witches cursed the play. Some say that Shakespeare himself cursed the play so that no one but he would be able to put on a performance of the play. Others still say that King James, for whom Shakespeare had written the play to impress, did not like the play very much. Ashamed, Shakespeare would not talk about MacBeth openly, instead calling it “That Scottish Play.” Speaking the name of the play, the names of the characters, and in some places directly quoting lines from the play, are all considered bad luck.
According to the site, productions of MacBeth are often accompanied by accidents and death. Other theatres that put on the production will sometimes go out of business soon after. MacBeth is, however, a more expensive production than most, and has more stage combat and special effects (old timey theatrical effects) than most plays, leading to the business failures and accidents, respectively.
If someone does speak the name “MacBeth” or quotes lines from the play, they are to exit the theatre immediately. The offender must then spin around three times and then knock on the door. The offender may not re-enter the theatre until someone lets them in.