AdWords is often conducting limited tests. Seo Roundtable caught a screenshot of one of the tests where Google is showing ads at the bottom of the SERPs, similar to what Yahoo does on their search result pages.

It’s pretty common to catch a glimpse of tests, such as the Google Click to Call.

Most of the tests are never implemented, but as their revue is based upon advertising, the mantra is test to see what users like.

Screen shots here.