I recently learned that, as of September, Adsense removed the "3 banners per page" limit:
My message board has a lot of pages that are very, very long (eg, 2,000 - 50,000px height), so I could fit a lot of banners on the side without distracting from the content. I currently have one 300x250 above the fold, followed by a 300x400 block of local content, followed by a second 300x250 below the fold, and a leaderboard at the bottom of the page, so those long pages have a lot of empty white space.
My question is, if I fill in that empty space with more and more banners (generated dynamically, of course), do you think that the increased banners will all help to increase the revenue substantially? Or will it lower the value of my existing banners, making the whole thing more or less irrelevant?