Yesterday, during the PubCon keynote Hot Google Topics & Trends Matt Cutts & Amit Singhal Matt Cutts made a point to talk about what changes in the algorithm will be happening in 2012.
One change that stood out was that content position on a page is going to be a ranking factor. He said "GoogleBot is getting smarter" and that determining the position of the content on the page, like what is above the fold - will be a factor. He added having a lot of ads in annoying spots can hurt the page.
Danny Sullivan covered this immediately with the title Google May Penalize Ad Heavy Pages, writing:
Ever encountered an ad-heavy page, where you struggle to find the actual content on that page? Google's looking at penalizing those in its search results.
The concept of looking at what is content is in which position of the page is not new. We discussed it in 2004 with Block (Passage) Level Link Analysis from Microsoft (back then, MSN Search). We also mentioned in in 2009.
Google will now look at this more carefully. So if you have ads in annoying spots, like where users expect to see content. I bet it will have a serious impact on that page's rankings in Google.
So be prepared!
Forum discussion at Google Webmaster Help.