"The designer, Brenden Macaluso, also mentioned that there's been some concern over the safety of using cardboard -- but his reasoning with regards to the materials is that cardboard is more heat-resistant than many plastics, with a much higher fire and ignition point -- 258°C (496.4°F)and 427°C (800.6°F), respectively -- where plastics begin to melt at about 120°C (248°F)."

http://www.engadget.com/2009/02/05/recompute-a-closer-look-at-the-sustainable-cardboard-pc/