I don't think I'd allow it either, certainly not in the professional world, anyway. If it was community theatre I might think about it, but I'd probably still say no. Having said that, I did have an episode where a guy approached us about proposing to his girlfriend on stage during our late-night improv show (he wasn't a performer). We made it work - much easier in an improv show, the players "chose" him and his girlfriend out of the audience for a game requiring audience extras. He did surprise all of us a little when he started out with the words "xxxx, I know we've only been going out for a month but...." as he hadn't given us that piece of information - I could see the horror in the eyes of the players as they realised it could all go very wrong, but mercifully she said yes!