I also think they would be fun to yell at. There are certain insults and arguments that are really only appropriate to say to someone you are dating. Why should people in relationships have all the fun? I've practiced this with a Starbucks barista but it generally leads to confusion and I don't really feel satisfied in the end.
Starbucks guy: Good morning, what can I get you?
Me: I shouldn't have to tell you.SG: I'm sorry?
Me: You never listen to anything I say.
SG: [becoming increasingly uncomfortable] Coffee? Latte? What will you be having?
Me: Did you ever even care about me at all [glancing at nametag], Tom?
SG: Room for cream?
Me: I think we should go on a break, Tom. I'll be at Dunkin Donuts. Call me when you grow up.