Thanks Brinked. If you feel that some sites have recovered, what was the length of time between changes made, and detecting positive results?
It took me a long time to realize: rewritten content. As my site became larger it was inevitable that something written about in 2010, would also be written about in 2011, and over time content was effectively - but unintentionally being duplicated.
However this is still speculation. Until I see some positive results - I cannot be sure why the huge panda hit.