I thought I would put a more personal perspective on Paws post.

With reference to this:

1985-1987 -- Therac-25 medical accelerator.

Taken from here:http://archives.obs-us.com/obs/engli...s/stumble.html

That day, Cox was supposed to receive a short, low-intensity burst, but there was an unnoticed problem in the computer program controlling the machine. Whenever a technician set the machine for a heavy radiation dose, then quickly changed the setting in a certain way, the computer program lost the correction and retracted the machine's safety interlocks. No one knew of the flaw, even though it had resulted in deep radiation wounds to a patient in Georgia the year before.
The above is from a book called "Moths to the Flame: the seductions of computer technology"

You can read it here: http://archives.obs-us.com/obs/engli...rawlins/moths/ ( if you are interested )