The 2008 Australian study of remnant data contained on 2nd hand hard   disks: the saga continues
  This study looked for remnant data on enterprise level hard drives that were purchased through auctions. The drives were analysed for information, be it topical or formatted. In the event that drives were formatted, forensic tools were used to recover this data. This years study revealed a high level of not simply un-erased drives, but drives which contained information that related to critical infrastructure providers. That such a small sample size yielded such a high rate of un-erased drives is of considerable concern, and it may be necessary for the government to become involved. 
Craig Valli and Andrew Woodward
cs.CR