The theory is that special expensive equipment could possibly do such a recovery -- so the 3-day time limit, and measly $40 prize, isn't really responsive to the question.<p>Further, if you were an agency with the budget and equipment to do this, would you want the world to know?<p>They aren't testing what they're trying to test, and even a 100x reward and 10-year time limit wouldn't prove the negative, "that recovering data from a zeroed hard drive is impossible".<p>A seminal paper on the possibility -- but not the reality -- of such specialized recovery is Peter Gutmann's 1996 "Secure Deletion of Data from Magnetic and Solid-State Memory" [ <a href="http://www.cs.auckland.ac.nz/%7Epgut001/pubs/secure_del.html" rel="nofollow">http://www.cs.auckland.ac.nz/%7Epgut001/pubs/secure_del.html</a> ].<p>Guttman notes in an undated epilogue, however, that advances in data density and recording techniques since 1996 make any recovery from modern devices "unlikely". Still, the "Great Zero Challenge" provides very little in the form of real evidence about these questions.