Producing computers requires the mining, processing, and transporting of massive quantities of raw materials almost two tons of such stuff is required to produce the average desktop PC and monitor, according to a 2004 United Nations' study. The fabrication just of a single two-gram microchip causes more than 50 pounds of waste, some of it toxic.
On the consumer end, disposing of electronic waste is an immense problem. Every year, 100 million computers, monitors, and TVs become obsolete in the US, and this number is growing. Although a lot of this gear winds up in landfills (the US Environmental Protection Agency calls e-waste the leading contributor of lead to municipal waste), most of it is sent to Asia and Africa, effectively transferring the problem to poorer countries. Read full here