Assuming coins haven't moved since 2010 are lost is a poor assumption for at least some percentage of them.  Slashdot's first article on it was July 2010 and a lot of people got involved and started mining then and just mined into an address and left them. 

It reminds me of the (continual it seems) proposals to require coins to be moved in order to keep them - one should not assume that coins that are of X age are lost.