Lack of security when discarding old machines or drives - contain confidential information

In today's time, we store a huge amount of data on our computers and on the disk drives that they contain. A small fraction of such information is pretty confidential, whether it be customer information, credit card information, social security information, police records, and even more importantly, national security related information (such as military and intelligence agencies). Accessing such information when it is in the computers during operation is pretty highly controlled, with all manners of security controls, penalties for unauthorized access, and so on. However, when these computers are discarded, precautions are not taken and such information can be extracted (link to article):

A third (34 per cent) of discarded hard disk drives still contain confidential data, according to a new study which unearthed copies of hospital records and sensitive military information on eBayed kit.
A disk bought on eBay contained details of test launch routines for the THAAD (Terminal High Altitude Area Defence) ground to air missile defence system. The same disk also held information belonging to the system’s manufacturer, Lockheed Martin, including blueprints of facilities and personal data on workers, including social security numbers.