I believe there are various levels of Panda penalization, from my experience and research. There is the non-panda sites, then there the Panda'd sites. These consist of:
Scraper sites - web sites stealing/copying content from other sites in order to build their content.
Thin content sites - sites that consist of pages with little or no content, serving very little use to any visitor.
Similar content sites - sites that have variations of the same content on different pages.
Badly structured sites - sites that have not been developed well, creating duplicate pages, thin pages, and bad pagination, just through incompetence more than anything.
Having too many ads is not a factor, but a lot of the thin content and scraper sites, are likely to have a lot of ads. Hence the relationship.