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This concept involves a lot more than just viewing or displaying. It's probably one of the most natural UI technologies between man and machine. According to Wikipedia multi-touch technology has a 25-year history but until recently there has not been much talk about it in public. Bill Buxton has aslo compiled a very nice overview of the history of multi-touch. His page describes numerous research projects but very few commercial devices.
If you have not seen multi-touch displays in action then I really recommend taking a look at Jeff Han's Mutli-Touch Interaction Research page. There are pictures (the one posted here is also from his website) and more importantly a video demonstration of the capabilities of this technology. The video is also available at Google.
Surely touch-screens are nothing new and I'm certain all of my blog readers have used a simple touch-screen but multi-touch screens have still mostly remained an area for research & development... until now that is. If you have seen the Apple iPhone then you have seen one of the first consumer devices for the "average Joe" that incorporates a multi-touch display. Apple has clearly recognized the implications of this technology and is leading the way for innovation by putting this wonderful technology in the hands of users.