Trivial etiquette question - can he touch my laptop screen?
thingie: Well, I would just tell them not to do it, because the screen gets dirty and you have to either clean it all the time, or you can't see anything on it. It's not rude to say something like "Well, I'm sorry, but please, don't touch the screen, it gets dirty, ok?". At least I think so.Of course this is most likely very depending on the culture and place where do you live.