The main reason for recycling computers is to prevent harmful toxins from entering Landfill, either in the US or abroad. Computers (especially CRT screens) contain: Lead, Mercury, Cadmium, Fire retardants, Phosphorous. The plastics will not decompose over time and the units will eventually leech contaminants into groundwater and land, either in the US or abroad.
Hence, you might think recycling your computer is a great thing. The only problem is that many recycling companies are simply exporting computers to developing Countries as re-useable equipment. The only problem being that they are sending out the scrap as well, which has to be broken down in the most hideous of working environments. Even, then, there's the possibility that your old computer may just be worthless as scrap and could just be left in a landfill. Still, the way I see it is the west will eventually end up paying for our own greed. Chances are, there'll be a major medical problem due to our own e-waste- probably along the lines of lead or heavy metals causing birth defects. It'll then be down to the international red cross to sort things out- or maybe, China will close their borders to the west, just to hide the issue from prying eyes.
If you do intend to recycle your computer equipment, make sure that you use a UK limited Company, registered with the Environment Agency as a Waste Carier at the very least. If you're taking your computer to a Local council run recycling site, always remove the Hard Drive first, just to protect your personal information. If you're in the US, please stop being ignorant and start using the Basel Action Network, rather than the major exporters you seem so keen to support. There are numerous recycling companies operating in New York, Boston, Washington, Austin and Conneticut. These services cover the majority of Major Cities in the United States.
Here's some details of the recycling service offered by IT-Green, the computer disposal specialists.