if it can be enforced at rock shows it can certainly be enforced in a broadway theater. the first time i experienced this was at a jack white show at kings theater in brooklyn and i fully expected an outcry but maybe because it was made so clear in, if i remember correctly, more than one email leading up to the show there wasn't a peep. or, if there was, i didn't hear it. nor did it delay exiting the theater. needless to say the experience of a cell phone-free show was blissful.