Google is testing a new ad layout in the search results, with ads appearing at the top and bottom of the page instead of being displayed on the side. Take a look!
Three ads are displayed above the organic search results and four are displayed below. It's hard to say what exact implications this might have for advertisers, but such a change would seem to make it even harder to distinguish organic listings from paid ones.
Ads appearing at the bottom of the search results were spotted by some Google users about a week ago, though the first reports were of ads appearing only at the bottom of the search results, not both at the top and bottom.