Hi - I asked Apple about this .. One great thing about Passbook is that every Pass can be created especially for a specific user. It enables true one-to-one consumer engagement. You can send customized promotions directly to the pocket of an individual person.
This enables marketing promotions that are traditionally difficult - e.g. In restricted markets such as tobacco, alcohol, gambling etc ..
Apple told me that their approach is that if the promotion would normally be blocked in the App Store - eg distributing *********** - then it's not appropriate for Passbook. Otherwise it's *probably* ok.
If in doubt you should ask Apple ..
If someone complains to them that a specific Passbook promotion seems to be unsuitable or illegal - first the developer will get contacted (this is why they insist that the developer's name & contact info is included on the back of each Pass). If the problem persists Apple will revoke the developer license (necessary to obtain Passbook signing certificates) ..