is shaping up with several pieces on collecting - physical, digital or even imaginary, so here's a useful (and absolutely fascinating) article on the history of the hard disk
in American Scientist
The magnetic coating on the disks was made by mixing powdered iron oxide into paint, Johnson says; it was essentially the same paint used on the Golden Gate Bridge. To produce a smooth layer, the paint was filtered through a silk stocking and then poured onto the spinning disk from a Dixie cup.
The cost of storing a megabyte of data has fallen from $10,000/megabyte to a tenth of a penny - 'well below the cost of paper'. You can visit the Magnetic Disk Heritage Center
for more information, or ask yourself the question, How Much Information is There In the World?