Zivush - 1:49 pm on Aug 8, 2012 (gmt 0)

I assume that there's an indirect correlation between #of ads and ranking.
When removing ads, site speed increases.
A speedy site makes the visitors happier and they tend to stay longer and navigate more on the site.
Time on site and page/visit are direct signals to ranking - These are the factors that may impact site's ranking.