I have always been fascinated about how the unique characteristics of a medium define its design space.
“I see this as a core principle of higher order UX; to use the medium in such a way that the medium facilitates the delivery of the message instead of polluting it. It’s that pollution that brings about unanticipated consequences in what the user experiences. This is just as much a holistic experience problem as well as a nitty-gritty design and interaction problem.”
(Erik Flowers a.k.a. @Erik_UX)