Point on reward & punishment feedback is a really good point, darkpatterns comes to mind.
If IxD does not provide choices for action, there is no room for ethics: People act based on conditions, not on considerations of what should be done
This reactive behaviour is what UX practioners of gamification feel proud to do. It's disgusting to see them feel proud doing it, how come they feel no remorse doing it?. I too will have to do it in the near future, but I won't fucking have a glitter in my eye and a wide smile across my face doing it.