okay. so, really, whats the deal with plus ones? when do you have to give some a guest and when do you not have to? i know sometimes its obvious, like for younger guests... but what if you know a person isn't in a serious relationship and you know they will know everyone else at the wedding, so it isn't an issue of them being alone? should you still give them a plus one? do you have to? i'm just not sure how this all works.