Originally posted by Kunzite however this kind of solution is designed to allow you to use either SD or CFs, not for "extra" reliability.
I suppose the intent is also to allow owners moving from previous models that only used CF to gracefully transition to SD. Not a problem for Pentax, I think they have always been SD. But for users with a pocket full of CF cards it might make a difference.
I'm not sure I follow the logic on using two different card types for redundancy. Two different cards, yes. Unless the thought is the controller dies and thus either destroys one of the cards or just refuses to work. But surely if that happened it would affect both cards. From a theoretical view yes, having independent and different systems makes sense. But in this case we are talking about pretty much the same thing, two different media types but still the same thing. CF and SD readers on my computer are integrated on the same controller and USB port.
Now if you had a system that writes to the local memory card and also over WiFi sends the file to the cloud or a computer then maybe I see that as redundant.