Green has long been in and repurposing packaging accomplishes this feat like no other.
In June, Asus computer company will begin to ship one of its Mini ATX motherboards in a special cardboard box that can double, yes double as a PC case. A set of punch out holes works as ventilation ports, and a rear panel can be removed to house the PC Connectors and interfaces.
Asus has said that the box has an expected life span of a year, more than enough time for PC builders to find the perfect case.
Fire hazard? Maybe.