Exactly why I wrote this. I don’t think it rationalizes bad design at all :). Learning to swipe up/down/right/left may not be initially intuitive, but once you see it or learn it, you immediately get it and I find the products that work this way much easier and faster to use than most others. Just because there is a learning curve which is fastest when you have a friend show you something doesn’t make it bad design. Actually in case of mobile I argue it might be even better design — and certainly intentional design.