Discovery can be bad too. If you don't eat meat or pork or whatever, you often have to go through the menu in O(n) and look for your options. And then maybe it's a dish they've stopped making months ago, but printing new menus would have been to expensive. (OK, that won't happen at McDonald's.)

With a tablet, you could filter the list with a single tap. I've thought about building such an app a few years ago because I'd love to use it, but I have no idea how you could sell it to restaurants. It seems most places are too conservative and cash-strapped to tie themselves to proprietary tech.