Don Norman: Why tablet and smartphone interfaces suck
OK, Norman didn't put it quite like that. The actual title of his article is Gestural Interfaces: A Step Backwards In Usability.
Don't let it throw you. As you'd expect from a usability expert, the article is highly readable. And it details why too many touch-screen interfaces suck: Buttons that don't exactly do what you think they might (or do more than you expect, like the back button that, hit once too often, takes you out of the application), mystery gestures that work in some cases but not others, ignorance of conventions such as what check boxes are supposed to do versus radio buttons, etc.
This isn't arcana. It's important stuff to think about as we enter the mobile era. Some of us are involved in design directly (not me, of course, but some of us here), while others of us have to (or at least should be) thinking about these things as we fashion content to interact with these systems.
Norman is one of the highly regarded usability researchers (partner of Jakob Nielsen).
In fact, I'd recommend taking a look at his whole jnd.org site. Some fascinating stuff about design and human-computer interaction, which I believe is too important to be left to the engineers. With the "printing press" effectively pushed to the desktop in many cases, journalists now have a dog in this hunt.