deadsea - 10:42 am on Aug 11, 2011 (gmt 0)
Yes. One of my sites put the entire footer boiler plate into an iframe at one point. The iframe was in robots.txt. When you searched for the text in the footer on Google, our site could not be found.
I'm not convinced that hiding content from Googlebot will ever hurt you. Ads are a type of content that Google *wants* you to hide from Googlebot. Google gives us many tools to hide portions of the site from Googlebot (robots.txt, noindex, nofollow). Using these judicously seems like fair play to me.