If you want to experience the world's biggest multitouch and multi user screen you have to visit the newly revamped Nürburgring in Germany. The Formula One race track has transformed into a theme park.
The two-piece so called ring°wall consists of an LED display and a multitouch information wall with a total surface of 425 square meters, which equals more than 6,000 computer displays.
Laser technology is used to track the touch inputs of more than 80 users. You can watch a video of the giant touchscreen below.
More details on the Vimeo page of this video and here you can watch the making-of. The ring°wall was built by German company Sensory Minds (site). Thanks CDog for the Tip.

See also the Nurburg Ring site.

ring°wall from SENSORY-MINDS on Vimeo.