David Harry has an excellent write up on the SEO implications of page segmentation. In short, the piece goes over how search engines can, and probably do, look at each web page and segment the page into components. For example, they can pull out the navigation, footer, ad blocks, and so on from the main body copy.
This concept is far from new, it goes way back and we even covered it back in mid-2004 with Block (Passage) Level Link Analysis by MSN. It just makes sense, why treat the ads on the page the same way one would treat the body content. That is the purpose behind Text Link Ads new product inLinks.
This is developing into an extremely important aspect of state-of-the-art SEO that cannot be ignored with impunity. While it's anybody's guess (still) how much of this technology has already been implemented by the search engines, you can easily bet the farm that it'll happen rather sooner than later.
In any event, if this is a new concept to you, you may want to read up on it. If some search engines are not deploying this yet, then they likely will soon. It just makes logical sense.
Forum discussion at Sphinn.