Many of my pages on various sites were hit as they are all new sites and Im relatively inexperienced.
Some were hit for too many affiliate links on the page, while others were not. The amount of content on the site was irrelevant.
My sites/pages hit the hardest had not just too many ads in the header area (above the fold), but also had affiliate text links inside the content.
My sites/pages that just had a lot of ads in header area were not hit at all.
I find this interesting, because the pages that had just one single content text link were punished if the page had a lot of other image ads outside the content.
If your site isn't too spammy, Panda does not punish the entire site. It merely punishes specific pages on your site (Google has said this).
I plan on doing more split testing within individual pages to try to figure out Googles boundaries by the next Panda update.
Note: two of my sites not hurt actually had 5 amazon text links above the fold, but outside the content, and another adsense image ad.