Touch-screen displays are now common on mobile phones and compact digital cameras. They're most effective where space for external control is limited, though they have the potential for some novel and interesting uses too.
The advantage for the manufacturer is simpler manufacturing and the ability to design (and update) much more sophisticated user interfaces.
They haven't appeared much on higher-end cameras, though, with the exception of recent Panasonic G-series models, where a touch-screen display is used to offer a range of camera controls as well as touch-controlled autofocus and shooting.
Here, you touch the screen to set the focus point and take the picture. It's a very intuitive and novel way of taking pictures, though it does mean that you have to take one hand away from the camera body to use it, and it could for most users prove to be little more than a novelty that you soon get tired of.
Touch-screen control is good for manufacturers, but not necessarily so good for users. Lower-quality displays can be sluggish or vague, without the tactile feedback you get from buttons and dials. And if you're using gloves, a touch-screen display could prove very difficult to use.
