joost - 11:18 am on Oct 11, 2012 (gmt 0)

Is there any proof of this?

Fact that only certain pages on the same domain are hit (and no-one reports improvements later on), and others are not, is probably part of that proof, since each page is normally optimized for a certain keyword, or keyword set.

This is why I think it is important to find out if non-affected pages (and new pages) can better their rankings for other keywords then the ones penalized. That would form the rest of the proof.

Anyone?