Google has started to show ads beneath the search engine results pages as well as the usual spots (above organic search results and at the right side). The ads below the organic search results can be found on Google.cn.
Google repeats showing the first two sponsored ads again below the organic search results, in which the first two ads will require Google Adwords Quality Score high enough to rank above the organic search results. The third sponsored ad above the SERP does not seem to be eligible for an additional spot at the bottom.
For Google, the introduction of the bottom ads is another new way to further monetize from Adwords.
For Adwords advertisers, having 2 identical ads showed above and below the organic search results at the same time does not count as 2 impressions. With this new change, your trademark keywords on Adwords are most likely to be showed twice (above and below).