Zivush - 5:06 am on Sep 24, 2012 (gmt 0)

I have never stuffed keywords (repeated the same KW) on purpose, so I can’t tell but people guess that -
1. Since Panda and Penguin, a site ranking is taken as a whole. Poor/shallow pages might have a negative ranking impact on the other site’s sections (if they are linked).
2. Before Panda and Penguin, strong pages had a positive ranking impact on the other site’s sections (if they are linked).

That’s why so many affected sites deleted/merged pages and have taken a close look at quality, including over-optimization.
You never know how Google measures page quality as you don’t have their tools. For them, it’s a math science, while for us, it is subjective.