I wish I'd been able to see the annual Iranian American ta'arof competition. Ta'arof is a notoriously difficult concept to understand if you're not born into it. A good friend had lots of trouble when he moved to Iran accepting dinner invitations he shouldn't have.
Polite Iranian:Come to my house for dinner.
My friend: OK. How about next Tuesday?
Polite Iranian (looking shocked): Err.. Yes, come to my house for dinner.
My friend (repeating): I'm free next Tuesday.
Polite Iranian (stretching limits of politeness): Yes, please come to my house for dinner.
My friend (exasperated): It's either next Tuesday or never!
Ta'arof seems to cover so much of Iranian cultural codes and Westerners, even Iranian-Americans, can blunder through it without realising what should or shouldn't be accepted.
(There's more info about the event here.)